Tumamoc Hill Timeline


ca. 5,000–1,700 B.C.

Middle Archaic Multiple radiocarbon dates consistently show that the earliest maize was cultivated 4,100 years ago in the Tucson valley at the base of A Mountain and Tumamoc Hill along the flood banks of the Santa Cruz river. This date makes the Tumamoc Hill and the adjacent area the longest continuously habited site in the United States.

2100 B.C. and 50 A.D.

Early Agricultural (previously labeled the Late Archaic) About 2,500 years ago a village site is constructed on the mesa at the top of Tumamoc Hill during. The volcanic walls that encircle the top of the hill and the upper slopes for a cumulative 2.3 km, trincheras, were built during this period, making them the earliest known public architecture in Arizona.

400 to 550 A.D.

Tortolita phase This is the time period considered by some researchers to mark the beginning of Hohokam culture. Settlements shifted from the floodplain to adjacent river terraces and occurred in many other settings as well. Archeological evidence suggests that about 1,500 a large village for this time period was built atop Tumamoc Hill. The setting of the Tumamoc Hill village is unique, at least within the limits of current knowledge. No other known Tortolita phase settlement is on a hilltop, and no other is surrounded by massive walls.

700–1450 A.D.

Hohokam culture matured, dominated the Sonoran Desert, and then faded during this period. Tumamoc Hill was surrounded by Hohokam villages, but the hill itself was not occupied as a living space. The largest Hohokam village in the immediate vicinity of Tumamoc Hill continued to be where St. Mary’s Hospital is today site. Extensive Hohokam farming was undertaken at the base of the Hill, including an agave plantation on the plain now to the SE of Anklam and Greasewood roads.

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.

Late 1850s and early 1860s

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. First recorded use of Tumamoc Hill dates to 1862 or 1863 when a soldier in Company C, 32nd Infantry, inscribed his name and company on a rocky outcrop on a west-side bench.


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.

The Carnegie Desert Botanical Laboratory


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.


Andrew Carnegie founded and endowed the Carnegie Institution of Washington (since 2007 the Carnegie Institution for Science), an independent research organization that would increase basic scientific knowledge. Carnegie contacted President Theodore Roosevelt and declared his readiness to endow the new institution with $10 million. Dr. Frederick V. Coville, who in 1981 had visited Death Valley and became intrigued by its varied plant life, was now chairman of the Advisory Committee on Botany and a Principal Botanist of the US Dept. of Agriculture. Shortly after the founding of the Carnegie Institution, Coville proposed the establishment of a laboratory to provide facilities for the investigation of all facets of desert plant life and to determine the differences between desert vegetation and more tropical plants. The Carnegie Instition approved the proposal and set aside $8,000 for the lab and assigned Coville and Daniel T. MacDougal (director of New York Botanical Garden) 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 (link to Carnegie publication), Coville and MacDougal choose Tumamoc Hill and its surroundings as the site for the botanical laboratory. The Tucson Chamber of Commerce donated the Tumamoc Hill site, water supply, road, and electrical hookup for the Laboratory. Construction began on the lab’s first building designed by S. F. Forbes of Douglas, Arizona. W.A. Cannon becomes the Lab’s first resident investigator. The Desert Botanical Laboratory opened on 7 October 1903.


Daniel T. MacDougal was designated as the first Director of the Desert Laboratory, a post he held until 1928 at his official retirement. Based on high productivity in the first two years and the establishment of a new Carnegie Department of Botanical Research led to an expansion of facilities and staff in September 1905, including the hiring of Godfrey Sykes. This year is also of note due to Francis E. Lloyd, plant anatomist at Columbia University, purchase of a struggling magazine of popular botany, The Plant World, and becomes its editor, which he brings to the lab upon his arrival the following year. Likewise, during the spring of this year, Volney Spalding set out 19 perennial plant quadrats, each 10x10m, mapped all their individuals, and photographed them. Today, nine of these plots remain, making them the world’s oldest permanent plant quadrats.


The laboratory acquired additional land through leases and purchases, increasing its land holdings to nearly 880 acres. A building extension, started that same year on the east end of the existing laboratory, doubled the size of the facility and created a south-facing U-shaped building. This year also marked the construction of a 5-mile-long wood post fence around the entire 880-acre site to keep out grazing animals that were disturbing the experimental plots. This important act ceased grazing and quarry activities.


Dr. Forest Shreve and his wife Edith joined the staff.


About 50 ecologists meet in Chicago and found The Ecological Society of America. Seven of them are investigators of the Desert Laboratory. In 1920 the Ecological Society of America takes over The Plant World from the Desert Laboratory and re-names it Ecology. Until 1954, the masthead of Ecology acknowledged: “Continuing The Plant World.”


Due to economic problems, Carnegie funding was drastically cut and only a small staff, under the direction of Shreve, remained. Shortly there after the Carnegie Institution transfers the Desert Laboratory to the U.S. Forest Service.

U.S. Forest Service Management


The Carnegie Institution sells Tumamoc to the US Forest Service for $1. 


Under the US Forest Service, the laboratory grounds get little use. The few studies done are accomplished by University of Arizona faculty and students. The USFS invited the US Marine Corps to build and use training facilities on Tumamoc Hill. Uses allowed and Easements granted during the Forest Service yearsincluded: Two clay pits were dug at the western base of Tumamoc Hill to serve as a source of clay for fired bricks. There are no kilns on the property, but misfired and damaged bricks were brought back to the property and dumped and used to shore up wash crossings. The bricks in the dumps are mainly a type used in the 1950s and 1960s. 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 which remian in use today and have damaged the remains of the ancient village on the top of the Hill. The forerunner of today’s El Paso Natural Gas Co. received the concession to build a major pipeline through southern Arizona during the Carnegie years in 1933.

University of Arizona


The University of Arizona buys Tumamoc from the United States of America and assumes responsibility for the ecological reserve. 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 area mapped for saguaros by Spalding in 1909. Then they map, record, and measure the several thousand sagauaros in them. 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.


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.

2003 Centennial

The Desert Laboratory is 100 years old.


The southwestern 320 acres of Tumamoc were purchased from the State of Arizona for the direct purpose of research and conservation by Pima County.


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.


The original rain water harvesting system on the main laboratory building and the Sonoran Plant garden in its eves are re-established.