AD 850 to 1250
Chaco Canyon served as a major urban center of ancestral Puebloan culture. Remarkable for its monumental public and ceremonial buildings, engineering projects, astronomy, artistic achievements, and distinctive architecture, it served as a hub of ceremony, trade, and administration for the prehistoric Four Corners area for 400 years--unlike anything before or since.

1250 to Present
Members of affiliated clans and religious societies from Hopi and the Pueblos of New Mexico continued to return to Chaco on pilgrimages to honor their ancestral homelands.

1680
The Pueblo Revolt of 1680 briefly unified the Pueblo peoples of New Mexico and their allied neighbors, and expelled Spanish settlers from the Southwest.

1691
Spanish re-conquest forced Pueblo patriots into exile. Many took refuge with Navajo people living in the Dinetah region (northeast of Chaco), and the resulting cultural interactions included intermarriage; the exchange of ceremonial knowledge; and conflict and competition.

1700s
By the 1700s, what archaeologists recognize as Navajo settlement patterns were already well established in Chaco Canyon.

1774
A map produced by Don Bernardo de Miera y Pacheco identified the Chaco Canyon area as "Chaca." This term may be a Spanish translation of the Navajo word Ts‚koh, meaning "rock-cut" or "canyon"--or Tzak aih, meaning "white string of rocks" (the later refers to the appearance the sandstone atop Chacra Mesa). "Chaca" is believed to be the origin of both "Chacra" and "Chaco."

1823
As Jos‚ Antonio Viscarra led a military force west from Jemez Pueblo onto Navajo lands, he noted many fallen Chacoan buildings along the way. His route became a well-used trail for 40 years.

1849
The Washington Expedition, a military reconnaissance under the direction of Lt. James Simpson, surveyed Navajo lands, and wrote accounts of Chacoan cultural sites. The Kern brothers produced excellent illustrations of the sites for a government report.

1877
W. H. Jackson with the U.S. Geological Survey (led by Hayden), produced expanded descriptions and maps of the Chacoan sites. Jackson noted Chacoan stairways carved into cliffs. No photos were produced, because he experimented with a new photographic process at Chaco, which failed.

1888
Victor and Cosmos Mindeleff of the Bureau of American Ethnology spent 6 weeks at Chaco surveying and photographing the major Chacoan sites for a monumental study of Pueblo architecture. Their photographs documented vandalism and looting. These oldest known photos provide us with a starting point for determining the modern effects of visitation, looting, vandalism, and natural collapse on these sites.

1896
After excavating Mesa Verde cliff dwellings (1888) and other ancestral Puebloan sites in the Four Corners area, Richard Wetherill moved to Chaco to excavate sites.

1896-1900
The Hyde Exploring Expedition, led by George H. Pepper from the American Museum of Natural History in New York City, established full-scale excavations at Pueblo Bonito. Their main focus was the accumulation of artifacts for the museum collection, and numerous crates of artifacts from Pueblo Bonito were shipped to the museum, where they remain today.

1901
Richard Wetherill homesteaded land that included Pueblo Bonito, Pueblo Del Arroyo, and Chetro Ketl.

While investigating Wetherill's land claim, General Land Office special agent S. J. Holsinger described the physical setting of the canyon and the sites, noted prehistoric road segments and stairways above Chetro Ketl, and documented prehistoric dams and irrigation systems. His report strongly recommended the creation of a national park to preserve Chacoan sites.

1902
Edgar L. Hewitt of the School of American Research mapped many Chacoan sites.

1906
Edgar Hewett and many others helped to enact the Federal Antiquities Act of 1906. Our nation's first law protecting antiquities, the Antiquities Act was a direct consequence of the controversy surrounding Wetherill's work at Chaco. The law also granted new powers to the President, allowing him to establish Mesa Verde National Monument--and the following year, Chaco Canyon National Monument..

1907
Chaco Canyon National Monument was established on March 11, 1907, as Richard Wetherill relinquished his claim on several parcels of land he held in Chaco Canyon.

1910
Richard Wetherill remained in Chaco Canyon, homesteading and operating a trading post at Pueblo Bonito until his controversial murder in 1910. Chiishch'ilin Biy‚ charged with his murder, served several years in prison, but was released in 1914 due to poor health. Wetherill is buried in the small cemetery west of Pueblo Bonito.

1920
Edgar L. Hewitt of the School of American Research returned to Chaco to excavate Chetro Ketl.

1921-1927
Neil Judd of the National Geographic Society excavated several hundred rooms at Pueblo Bonito, as well as portions of Pueblo del Arroyo and several smaller sites for the Smithsonian Institution. One of his expedition's goals was to preserve the excavated Pueblo Bonito and it's empty rooms as a "monument to its prehistoric builders." The site received extensive preservation treatments, in which previously vandalized walls were repaired, walls were strengthened, broken masonry was patched, and missing door lintels were replaced.

1927
Frank H. H. Roberts excavated the pithouse village called Shabik'eschee. This site pre-dated the period of the construction of Chacoan great houses (monumental public buildings), and became the archaeological "type-site" (example) for the Basketmaker III period in the Pecos classification of Pueblo cultures.

1928-29
Dr. A. E. Douglas of the National Geographic Society applied the new method of tree-ring dating
dendrochronology) to Chetro Ketl and many other sites in Chaco Canyon.

1929-47
Edgar L. Hewett of the School of American Research and Donald D. Brand of the University of New Mexico field school excavated at Chetro Ketl and numerous small sites. No reports were published.

1933-1937
Gordon Vivian began major site preservation work, at Pueblo Bonito, Chetro Ketl, and Casa
Rinconada.

1937
A 200-person Civilian Conservation Corps camp was constructed near Fajada Butte. The group constructed extensive soil conservation devices (earthen berms), and planted 100,000 cottonwood, tamarisk, plum, and willow trees throughout the canyon, and improved many roads and trails. They initiated a project to build a vehicle road to the top of the cliff, directly above Pueblo Bonito, but World War II interrupted construction, and the project was abandoned.

A second Civilian Conservation Corps group began work at Chaco with an all-Navajo crew of stonemasons who repaired many of the large excavated Chacoan buildings, which were now threatened due to years of exposure to wind, rain, and freeze-thaw cycles. Preservation measures continue to this day, and several members of the NPS preservation crew are second-generation Chaco stonemasons.

1941
On January 21, 1941, after a year of heavy rains, Threatening Rock fell and destroyed about 30 rooms at Pueblo Bonito that had been excavated by Neil Judd in the 1920s.

1947
Tomasito, the last Navajo resident living in Chaco Canyon, moved away.
Monument boundaries were fenced to exclude livestock, and an era of rangeland recovery began.

1949
The University of New Mexico deeded lands in Chaco Canyon National Monument to the National Park Service, in exchange for continued rights to conduct scientific research in the area.

1959
The park visitor center, staff housing, and campgrounds were constructed during the National Park Service "Mission 66" construction boom (1956-1966).

1971-1982
The National Park Service and the University of New Mexico established the Division of Cultural Research or "Chaco Center" under the direction of Dr. Robert H. Lister and Dr. James Judge. Muti-disciplinary research, archaeological surveys, and limited excavations began. Chaco emerged as a regional center of ceremony, administration, trading, and resource distribution, where year-round residents may have been few, and others may have assembled temporarily for annual events and ceremonies. The Chaco Center extensively surveyed Chacoan "roads". The results of the Center's research at Pueblo Alto and other sites dramatically altered our interpretation of the Chacoan world.

1980
On December 19, 1980, Chaco Canyon National Monument was re-designated Chaco Culture National Historical Park. An additional 13,000 acres were added to the park. The Chaco Culture Archaeological Protection Site program was inaugurated to jointly manage and protect Chacoan sites located on Bureau of Land Management and Navajo Nation lands.

1987
On December 8, 1987, Chaco Culture National Historical Park was designated a UNESCO World Heritage Site, joining a select list of protected areas "whose outstanding natural and cultural resources form the common inheritance of all mankind."

1981 to Present
Archeological excavations in Chaco Canyon today are limited, because a major philosophical change in archaeology has shifted attention away from costly, large-scale excavations, and brought to the fore an important new concern about the belief of many Pueblo and Hopi Indians and others that these sites and the ancestral human remains should be left to naturally return to the earth without being disturbed.

Modern methods such as remote sensing now allow archaeologists to gather a great deal of information without ever disturbing sites. Sites are mapped and surveyed, and sampled for tree ring dating studies. Pottery sherds are studied and dated. Museum collections are re-examined. New ideas emerge from the existing data that has been collected over the last 100 years. The oral history traditions of Pueblo and Hopi Indian descendants provide researchers with complimentary insights and understanding of these sites. Efforts continue to focus on preserving the enormous backlog of excavated sites, using important techniques such as backfilling (re-burying rooms with sand).

1991 to Present
Chaco Culture National Historical Park inaugurated the Chaco American Indian Consultation Committee, and began consulting with affiliated American Indian pueblos, tribes, and governments, to help us better understand the history and the legacy of their Chacoan ancestors. Representatives now actively consult with the park on important management issues during bi-annual meetings, sharing their knowledge and history of the area with park staff and visitors, and providing valuable assistance with museum collections, site preservation, and public education.

2000-2001
The Chaco Synthesis Project , now in progress, will summarize archaeological work completed by the Chaco Project (1971- 1982). A series of five conferences and a final "capstone" conference will consolidate information concerning different aspects of Chaco archaeology. Subject-matter experts will produce two publications, and a popular publication will also be produced.