| 1848 | Gold discovered in California. Gila Trail becomes one of the main routes to the gold fields. |
| 1850 | Compromise of 1850 made establishment of the Territory of New Mexico possible. (Arizona was part of New Mexico Territory) |
| 1852 | Americans begin navigating the Colorado River by steamer. Army Corps of Topographical Engineers begins surveying Arizona. See also: "Early exploration routes into the Arizona area." (Froeschauer-Nelson, Peggy. Cultural Landscape Report: Hubbell Trading Post National Historic Site Ganado, Arizona) |
| 1853 | Gadsden Purchase gives Arizona the land from the Gila River to present boundary. See also: Gadsden Purchase of 1853 and History of Arizona: Gadsden Purchase. |
| 1854 | First American mining (commercial) ventures. |
| 1856 | American Dragoons (cavalry) occupy Tucson; Arizonans begin petitioning for separate territorial status. |
| 1857 | Beale's camels and "Jackass Mail" stagecoach lines cross Arizona; Fort Buchanan established on Sonoita Creek. |
| 1858 | Butterfield Overland Stage Line crosses Arizona. See also: "Early stage routes through the Arizona area." (Froeschauer-Nelson, Peggy. Cultural Landscape Report: Hubbell Trading Post National Historic Site Ganado, Arizona) |
| 1860's | Period of gold discoveries, Gila River, Colorado River, and Bradshaw Mountains. |
| 1861 | Bascom Affair pits Army against Chiricahua Apaches; Civil War begins and U.S. military posts are abandoned in Arizona portion of New Mexico Territory. |
| 1861-1886 | Apache Wars. See also: Cochise: Native American leader (1812-1874) and Biography of Geronimo |
| 1862 | Arizona becomes a Confederate territory; Battle at Glorieta Pass, New Mexico, ends Confederate westward thrust; Battle at Picacho Pass, near Casa Grande, is called westernmost battle of Civil War; California Column occupies Arizona for Union; Battle of Apache Pass between Column and Apaches is largest in Arizona history; Fort Bowie is established in the Pass. |
| 1863 | Territory of Arizona is established; President Abraham Lincoln appoints Arizona Territorial officials; John A. Gurley is named governor; dies August 18. John N. Goodwin replaces him; Territorial officials take the oath of office at Navajo Springs, Arizona on December 29; Walker Party discovers gold in Bradshaw Mountains; Weaver-Peeples party discovers placer gold at Rich Hill; Wickenburg finds rich lode at Vulture Mine. See also: A History of Mining in AZ. |
| 1864 | Territorial capitol moves from its provisional site at Camp Whipple to Prescott; four counties (Yuma, Yavapai, Pima and Mohave) are created; Navajo take "long walk" to Bosque Redondo, New Mexico. |
| 1867 | Territorial capitol moves from Prescott to Tucson. |
| 1869 | John Wesley Powell explores Grand Canyon. |
| 1870's-1880's | Age of Silver; open range cattle industry flourishes. See also: Preliminary report concerning explorations and surveys, principally in Nevada and Arizona. |
| 1871 | Camp Grant Massacre. |
| 1872-1873 | General Crook subdues central Arizona Apaches and Yavapais. |
| 1876 | Territorial prison opens at Yuma. |
| 1877 | Territorial capitol moves from Tucson back to Prescott; silver discovered at Tombstone; copper deposits found at Bisbee. |
| 1881 | City of Phoenix incorporates; Southern Pacific Railroad crosses southern Arizona. See also: The Promise of Gold Mountain. |
| 1883 | Atlantic & Pacific (Santa Fe) railroad crosses northern Arizona. |
| 1888 | Copper replaces gold and silver in economic importance in Arizona. |
| 1889 | Territorial capitol moves from Prescott to Phoenix; Legislators meet temporarily in the chambers of the Phoenix City Hall. |
| 1891 | Moses H. Sherman and Marcellus E. Collins of Phoenix donate ten acres of land for a territorial capitol site. |
| 1895 | Phoenix linked by rail to northern and southern railroad lines. |
| 1898 | Rough Riders fight in Cuba. See also: William Owen O'Neill and Buckey O'Neill. |
| 1899-1900 | Construction begins on a new capitol building in Phoenix; completed in 1900 at a cost of approximately $136,000. |
| 1901 | Capitol building dedicated on February 25. |
| 1902 | Frank Murphy builds "Impossible Bradshaw Mountain Railroad." |
| 1903 | Salt River Water Users' Association formed, first of its kind in the nation. |
| 1906 | Referendum on joint Arizona-New Mexico Statehood is rejected in Arizona by a vote of 16,265 to 3,141. |
| 1910 | Arizona Enabling Act passed by Congress; Constitutional Convention meets; population of Arizona exceeds 204,000 on the eve of statehood. |
| 1911 | Theodore Roosevelt Dam completed; President Taft vetoes admission of Arizona over recall of judges; Arizona agrees to make the necessary changes in its constitution. |
| 1912 | Arizona joins the Union on February 14; George W. P. Hunt, President of the Constitutional Convention, becomes first state Governor; first U.S. Senators, Henry F. Ashurst and Marcus A. Smith; U.S. Representative, Carl Hayden. |
| 1912 | Women gain right to vote in Arizona. See also: History of Women's Suffrage. |
| 1917 | WWI brings economic boom to Arizona. Labor unrest in Bisbee brings deportation of suspected radical I.W.W. Union members by locals. |
| 1929 | Great Depression lasts into late 1930's. |
| 1936 | Hoover Dam on the Colorado River is dedicated. See also: PBS film The American Experience: Hoover Dam |
| 1941-1945 | World War II brings economic boom to Arizona; cotton, copper, cattle, farming and industry flourish. |
| 1946 | Arizona right-to-work becomes effective; industrial development and manufacturing take on new importance. Post-WWII brings surge of population to Arizona. |
| 1948 | Motorola builds first plant in Phoenix marking the beginning of high tech industry in Arizona. |
| 1948 | Arizona Indians gain right to vote. |
| 1950 | Election of Governor Howard Pyle gives rise to Republican Party. |
| 1960 | Arizona population exceeds 1 million. |
| 1961 | Stewart Udall becomes first Arizonan to serve on Cabinet (Secretary of Interior). |
| 1963 | Arizona wins Supreme Court decision in contest with California over share of Colorado River water; hopes are revived for a Central Arizona Project to bring water from the Colorado to central Arizona. |
| 1964 | Arizona's U.S. Senator Barry Goldwater is the Republican Party candidate for President. |
| 1966 | Legislative reapportionment (one man, one vote). Legislative districts reapportioned to represent an equal number of people. The Republican Party gains control of the legislature for the first time. |
| 1968 | Authorization is given for construction of the Central Arizona Project; Senator Carl Hayden retires after serving Arizona in Congress since 1912. |
| 1981 | Sandra Day O'Connor becomes first woman on U.S. Supreme Court. See also: Library of Congress: Resourceful Women |
| 1984 | Population of Arizona exceeds 3 million. |
| 1985 | Central Arizona Project brings water to state's interior. |
| 1988 | Impeachment of Governor Evan Mecham. |
| 1988 | Rose Mofford becomes Arizona's first female governor. |
| 1992 | Arizona becomes first state to have voter approval of a paid Martin Luther King Jr./Civil Rights Day state holiday. |
