The past exists for one overriding purpose: to prepare us for the future. It is the great and wise teacher.
— Leonard J. Pitts Jr. (20 Feb 2011)


ca. 2500 years ago

Indigenous peoples build a town on the mesa at the top of Tumamoc Hill during the Cienega phase (500 to 300 B.C.). They surround it with a trinchera, a massive, rubble-laid wall of native volcanic rock.

ca. 1500 years ago

After the Tortolita phase (A.D. 400 to 550), the upper town is abandoned as a residence site and it becomes a place of ceremony and pilgrimage.

Pre-Columbian millennium

Extensive Hohokam settlement and farming occurs at the base of the Hill, including an agave plantation on the plain SE of Anklam and Greasewood roads. The Hohokam leave relics all over the area, including handsome petroglyphs and pottery fragments. At some point, Tumamoc settlement and farming can be classified as Piman. Today's Tohono O'odham Nation are the direct descendants of these people.

ca. 1450

The Tohono O'odham move their area of settlement southward away from Tumamoc, but they and other Arizona tribes maintain their spiritual connection to Tumamoc Hill.

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Early Tucson


The Mission San Agustin de Tucson is established on the west bank of the Santa Cruz River near Tumamoc Hill.


Hugo O'Conor establishes El Presidio de Tucson east of the Santa Cruz River. The modern city of Tucson is born.

ca. 1858

Cattle grazing begins on and around Tumamoc Hill. Goats, burros and horses also graze freely. Soon, quarrying of Tumamoc's basalt begins to supply Tucson with native rock for building homes, walls and other structures.


The Southern Pacific Railroad reaches Tucson. Railroad executives appeal to the bishop of Arizona for a hospital in Tucson. The Sisters of St. Joseph of Carondelet establish St. Mary's Hospital at the foot of Tumamoc Hill.

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The Desert Lab


Frederick V. Coville visits Death Valley and is intrigued by its varied plant life (Science 20: 342). He wonders how plants could possibly manage in such heat and aridity.


With the blessing of President Theodore Roosevelt, Andrew Carnegie establishes and endows The Carnegie Institution to conduct scientific investigations. Coville, by then Principal Botanist of the US Dept. of Agriculture, appeals to the Institution to set up a botanical laboratory in the desert. Purpose: to discover how plants manage to survive and thrive in hot, dry environments. The Carnegie sets aside $8,000 for the lab and delegates Coville and Daniel T. MacDougal to find a suitable place for it.


After an overland journey that takes them to promising sites in California, New Mexico, Chihuahua and Sonora, as well as Arizona, Coville and MacDougal choose Tumamoc Hill and its surroundings as the site for the botanical laboratory. The Tucson Chamber of Commerce arranges to buy and lease 880 acres as a scientific reservation for The Desert Botanical Laboratory. W.A. Cannon becomes the Lab's first resident director. Its first building ready, The Desert Botanical Laboratory opens on 7 October. Prof. Volney M. Spalding of the University of Michigan visits the DBL and asks to be allowed to work there. Spalding is a noted forest conservationist and taught the world's first true forestry course at Michigan in 1881. He is also a botanist and wants to contribute to the investigation of how plants get along despite desert heat and dryness.


The Carnegie Institution of Washington is chartered by the Congress of the United States of America.


Desert plant physiological ecology is born on Tumamoc. It continues to be practiced here to this very day. The earliest review is Burton Edward Livingston's (1906. The Relation of Desert Plants to Soil Moisture and to Evaporation. Publication No. 50, The Carnegie Institution of Washington, Washington DC).


Mrs. Effie S. Spalding, an accomplished botanist in her own right, publishes one of the first research papers done on Tumamoc (Spalding, Effie S. (1905) Mechanical adjustment of the sahuaro to varying quantities of stored water. Bull. Torrey Botanical Club 32: 57-68). She shows that the stems of saguaro cacti expand when water becomes available, and contract as it is used. That explains why the stems of saguaros, as well as many other cacti, are pleated like an accordion.


Francis E. Lloyd, plant anatomist at Columbia University, buys a struggling magazine of popular botany, The Plant World, and becomes its editor.


During the springtime, Volney Spalding sets out 19 perennial plant quadrats, each 10x10m, maps all their individuals, and photographs them. He puts them in every discernable habitat in the Tumamoc reservation. Today, nine of these plots remain. Spalding's permanent plant quadrats are the world's oldest.


The Tumamoc Ecological Reservation becomes a restoration ecology project, the world's first. To protect Spalding's growing vision of Tumamoc as a place to observe the recovery of natural vegetation and to embark on a long-term study of the structure and function of plant associations in the complex desert landscape of Tumamoc, The Carnegie funds a 5-mile-long, barbed-wire fence to encompass the entire 880-acre reservation. Grazing ceases. Quarrying is also halted. "Within a few months after the completion of this fence" the investigators notice a change in "the vegetation and that of the surrounding areas..., and also an increased abundance in the number of the wild animals." To help Spalding's investigations, Prof. Tolman, University of Arizona, and his students, map the entire reservation, and Prof J. J. Thornber, University of Arizona, gives the Lab a set of herbarium specimens.


Francis E. Lloyd moves briefly to the Desert Lab. In less than a year, he solves the riddle of how plants control the openings that allow them to exchange oxygen and carbon dioxide without losing too much water. He also brings The Plant World, his struggling horticultural magazine, along.


Lloyd leaves the DBL in 1907, leaving his journal and its mounting debts behind. Livingston becomes its editor and MacDougal, now resident director, undertakes to put the journal on a sound financial footing. The Plant World becomes the journal where much of Tumamoc's research is published.


Spalding becomes editor of The Plant World.


With the help of a poor guy named Jacob Blumer, Spalding sets out to tag and map every last giant cactus on the reservation. During the first year, they succeed in doing between 10,000 and 15,000 saguaros. Blumer quits, unappreciated, and the effort is abandoned. Meanwhile, the data show Spalding that Tumamoc has very few saguaro seedlings. Spalding worries about the future of the species. His concern eventually leads University President Homer Shantz in 1928 to begin saving land on the west side of the Rincon Mts., an area that was dense with saguaros. Shantz's project expands to become Saguaro National Park.


Forrest Shreve takes the baton from Volney Spalding. He becomes editor of The Plant World and agrees to continue collecting data from the permanent quadrats.


Shreve adds a 557m2 permanent study plot (still used occasionally) and censuses its perennials.


About 50 ecologists meet in Chicago and found The Ecological Society of America. Seven of them are investigators of The Desert Laboratory. Forrest Shreve becomes the Society's first treasurer and takes on the job of shepherding the ESA in all western states.


The Ecological Society of America takes over The Plant World from Shreve and The Desert Laboratory. It becomes Ecology. Until 1954, the masthead of Ecology proudly acknowledged: "CONTINUING THE PLANT WORLD."


Shreve sets up another eight permanent quadrats in the bajada southwest of the mesa where he found soil different from any included in other quadrats. Still used, these quadrats are adjacent to each other, forming equal 10x10m subdivisions of a 20x40m rectangle.


A few Desert Laboratory stalwarts take lunch at the Old Pueblo Club on 7 October to celebrate the thirtieth birthday of the laboratory. Indicative of the Great Depression and diminished support from The Carnegie Institution, no one from Washington attends.


Tumamoc grants its first public utility easement. The forerunner of today's El Paso Natural Gas Co. builds a major pipeline through southern Arizona to deliver natural gas to the region for the first time. It traverses some 1,800 feet of the reservation. Shreve is unhappy but finally relents after obtaining some needed adjustments to the easement. The EPNG of 2008 has become a valued partner of Tumamoc in resolving issues that threaten research on the reservation.

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Forest Service years


The Carnegie Institution sells Tumamoc to the US Forest Service for $1. But The Carnegie had not forgotten its mission nor entirely abandoned its advocacy. The President of The Carnegie, Dr. Vannevar Bush, to C.L.Forsling, Asst. Chief, US Forest Service (16 Mar. 1940): "The Institution wishes to stress the desirability of maintaining the fenced-in land as a demonstration area of natural conditions for future studies." This in response to a Forsling to Bush letter (20 Feb. 1940): "...the Forest Service would immediately assume custodianship and protection of the entire area of some 900 acres. Its policy would be to keep the area enclosed and otherwise protected from domestic livestock use."


Under the aegis of the US Forest Service, the reservation gets little use. The few studies done are accomplished by University of Arizona faculty and students. Meanwhile USFS invites the US Marine Corps to build and use training facilities on Tumamoc Hill. It also re-establishes quarrying in the form of a clay pit for brick making, allows the construction of damaging roads, and — especially in the 1950s — indulges in a flurry of easement-granting that has left the reservation scarred and damaged the remains of the ancient village on the mesa top. But, they did maintain that fence, just as they had promised! We are still The Tumamoc Ecological Reservation.

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UA buys Tumamoc


The University of Arizona buys Tumamoc from the United States of America and assumes responsibility for the ecological reservation. In the deed, the UA promises to use it solely for research and education.


J.R. Hastings and Ray Turner of the USGS re-establish the old Spalding saguaro study. They survey four large tracts, each 250 m wide, within the old saguaro area. Then they map, record and measure every sagauaro in them. There were many thousands. These tracts were recensused in 1970 and 1993. They remain in use today, Turner and some new colleagues (including Bob Webb of USGS and Larry Venable of UA) having most recently surveyed them in 2011 & 2012. These patient and prolonged studies show that saguaros reproduce sporadically, with decades of failure in between. Today we know that the cactus is flourishing on Tumamoc Hill.


The US Secretary of the Interior designates the Desert Laboratory a National Historical Landmark. Volney Spalding's quadrats and three of the laboratory buildings are listed in the designation.


The State of Arizona designates Tumamoc Hill as a State Scientific and Educational Natural Area for its biological excellence.


D. Lawrence Venable establishes an extensive set of new permanent plots to study the annual wildflowers of Tumamoc Hill. For some species in these plots, he now has 30 plant-generations of observations and data!


The US Secretary of the Interior extends Tumamoc Hill's National Landmark designation to cover the entire 860-acre ecological reservation.


Governor Rose Mofford officially sets aside 200 acres of State Trust Land on behalf of The University of Arizona to use for research. This land — part of the original land grant received by the University when it was established — had always been within Tumamoc's fenced border.


Centennial — The Desert Laboratory is 100 years old.

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Turning the page


Joaquin Ruiz, Dean of the UA College of Science, forms The Alliance for Reconciliation Ecology on Tumamoc Hill. The Director of the Alliance, Michael Rosenzweig, is also charged with the responsibility for directing the Desert Laboratory.


Dean Ruiz creates an umbrella called Tumamoc: People and Habitats. Its divisions are The Desert Laboratory; The Alliance for Reconciliation Ecology; and the archeological activities plus cultural obligations incumbent upon a University that fully respects the past and its treasured legacies.

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The school trustland


The southwestern 320 acres of Tumamoc was a political football for a century. Who should own it was clear — the Hill's research operation (which, for decades, rented it for research from the state). But who did own it was even clearer — legally it had to be the property of the Arizona State Land Trust, to be used exclusively for the benefit of K-through-12 education in the state. Owing to a bond approved by the people, and to an extraordinary confluence of the economic stars, and to a substantial number of strong and courageous political leaders (including Councillor Regina Romero and Pima County Supervisor Richard Elias), Pima County buys the 320 acres at auction on 23 February and the City of Tucson accepts ownership of some 20 acres that are severely damaged environmentally.


On April 5th, the Department of the Interior of the United States entered the 860-acre Tumamoc Hill Archaeological District into the National Register of Historic Places.

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A portion of the massive trinchera at the top of Tumamoc Hill.

Hohokam petroglyphs

Hundreds of ancient Hohokam petroglyphs remain on Tumamoc Hill.

The famed tuberculosis sanatorium of St. Mary's Hospital about 1900. It had a revolutionary open interior gallery that permitted all patients to enjoy fresh, warm Tucson air.

The Main Building. Built in 1903 and enlarged in 1906. It now houses administrative offices, a refurbished library and a large classroom.

Burton Livingston invented a rain gauge to measure rainfall in remote localities. It used a film of heavy oil to protect the rain water from evaporation until the investigator — who could check it only rarely — made his rounds and recorded its depth. Simple? Yes, but it opened vast areas of the southwest for collection of accurate weather data.

Effie Spalding measures the distance between the ribs of a saguaro.

A microphotograph made by Francis Lloyd in 1906 of a stomate (Greek for mouth) in the surface of a plant leaf. The black bodies that surround the opening allow the plant to open and close the football-shaped hole in the middle. That, in turn, allows the plant to regulate its exchange of oxygen and carbon dioxide with the air outside.

Forrest Shreve (left) and Burt Bovee on a research trip to Marshall Gulch in the Catalina Mts. about 1910.

'CONTINUING THE PLANT WORLD' The cover of Ecology proclaimed its Tumamoc roots from its beginning in 1920 until 1954.

EPNG engineers and Tumamoc scientists devise a way to test the 1800-ft gas pipeline from 1933 while preserving the environment of the Hill and its research. Cutting the ribbon to open the project on a hot 22 August 2008 are (from the left) UA Pres. Robt. Shelton, Tucson Councillor Regina Romero, Pima County Supervisor Richard Elias, US Rep. Raúl Grijalva, Tumamoc Director Michael Rosenzweig and EPNG's Loren Locher.

After WWII, the US Forest Service built this native stone structure on Tumamoc Hill to house its Southwestern research unit.

In 2011, Ray Turner and Bob Webb install a spring-loaded brass band to measure changes in saguaro diameter after each rain event.

US Dept of the Interior declares the 'Desert Laboratory' a National Historic Landmark in 1976.

A springtime display of Arizona annuals.

Joaquin Ruiz

Pima County buys the southwestern 320 acres of the Tumamoc reservation at public auction, 23 February 2009. Four very interested, very happy parties pose afterwards, relishing the victory. From the left: Christina McVie (Board chair of the Coalition for Sonoran Desert Protection); Pima County Supervisor Richard Elias; Tucson Councillor Regina Romero; Tumamoc Director Michael Rosenzweig

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