The earliest inhabitants of Arizona, some archeologists believe, were prehistoric peoples who roamed the American southwest about 20,000 years ago. In the centuries that followed, their descendants or successors reached a high level of development. Among these were the Hohokams, who built canals in the desert region, and the Anasazi, or Basketmakers, who constructed cliff dwellings in the upland country. The present-day tribes had emerged by the time Columbus discovered America.

Important dates in Arizona
1539 Marcos de Niza, a Franciscan priest, entered what is now Arizona.
1540 Francisco Vásquez de Coronado led a Spanish expedition into the region.
1776 Tucson was established as a military outpost.
1821 Arizona became part of Mexico.
1848 Following the Mexican War, Mexico ceded to the United States most of what is now Arizona.
1853 The United States and Mexico signed the Gadsden Purchase, which added more land to Arizona.
1863 Congress created the Arizona Territory.
1912 Arizona became the 48th state on February 14.
1936 Hoover Dam was completed.
1948 Arizona Indians received the right to vote.
1974 Construction began on the Central Arizona Project to provide water from the Colorado River to the state's needy areas. Project completed in 1991.
1975 Raul H. Castro became the first Mexican American governor of Arizona.
1981 Arizona Judge Sandra Day O'Connor became the first woman appointed to the U.S. Supreme Court.
1988 Governor Evan Mecham was removed from office. He was replaced by Secretary of State Rose Mofford, the first woman to serve as Arizona's governor.
1991 Central Arizona Project completed.
1997 Arizona Governor Fife Symington resigned.
1998 Jane Dee Hull, who had replaced Symington, was elected to a full term. She thus became the first woman to be elected governor of Arizona.