Casa Grande Ruins Casa Grande Ruins National Monument, Arizona: A Centennial History of the First Prehistoric Reserve 1892 - 1992

Casa Grande Ruins National Monument lies within the basin and range area of southern Arizona which is a part of the Sonoran Desert. The mountain ranges around the monument are pre-Cambrian granites and schists. Some are cut by younger granitic rocks and flanked by tertiary lava flows. The nearly level plains between the mountain ranges contain Sonoran Desert scrub characterized by creosote bush — bursage vegetation. The monument elevation ranges from 1427 feet in the southeast corner to 1414 feet on the northwest side. Casa Grande is on the drainage of McClellan Wash, a tributary of the Gila River. Its soil is Coolidge sandy loam with caliche, a limy hardpan, two to four feet below the surface. The monument's biotic community is surrounded for the most part by irrigated agricultural land. There are sixty documented archeological sites in the monument. Some of these sites have been dated to AD 550-700, while the compounds were built between AD 1200-1450.

Casa Grande Ruin Reservation was created on June 22, 1892 by order of President Benjamin Harrison to protect a one-of-a-kind remaining Casa Grande or Great House. As a result, Casa Grande became the first prehistoric and cultural site to be established in the United States. The 480 acre reservation boundary changed in 1909, but retained the same acreage. An act in 1926 reduced that area to 472.5 acres. Some controversy has occurred over the years about the exact name of the monument. Originally, it was set aside as Casa Grande Ruin Reservation. In 1918 President Woodrow Wilson proclaimed it to be Casa Grande National Monument. Subsequent congressional acts in 1926 and 1930 called it Casa Grande Ruins National Monument. Some National Park Service personnel have held that the national monument proclamation of 1918 should determine the name, but, on the basis of the later legislation combined with a legal opinion and desire by monument management to be known as Casa Grande Ruins National Monument, the National Park Service Chief Historian recommended on December 17, 1991 that it be recognized as Casa Grande Ruins National Monument.