The Senate approved the Treaty of Guadalupe Hidalgo, ending the Mexican-American War. Under the terms of the treaty, Mexico ceded a vast amount of territory to the United States, including about 70 percent of present-day Arizona.
The Senate passed the act organizing the New Mexico Territory, which included much of present-day Arizona. The act was the first of five known collectively as the Compromise of 1850.
U.S. Minister to Mexico James Gadsden negotiated with Mexico leader Santa Anna to purchase more territory, including the remaining 30 percent of Arizona. This became known as the Gadsden Purchase.
The Senate passed legislation organizing Arizona as a separate territory. Four days later, the president signed the bill.
President William Howard Taft vetoed a joint resolution for the admission of Arizona to statehood because he objected to a provision in the Arizona constitution permitting the recall of judges. In December the people of the territory voted to remove the recall provision but after admission to statehood in 1912, the voters reinstated the provision.
Arizona became the 48th state in the Union.
Henry Fountain Ashurst of Prescott and Marcus Smith of Tucson presented their credentials, took the oath of office, and were seated as Arizona's first United States senators. Both had been elected by the state legislature on March 26. The senators then drew lots to determine their class assignments. Senator Ashurst drew Class 1, with a term to expire March 3, 1917. Senator Smith drew Class 3, with a term to expire March 3, 1915.
Carl Hayden of Phoenix, who had represented Arizona in the House of Representatives since 1912, began his Senate career. Hayden became Arizona’s longest-serving senator on December 11, 1955, surpassing Henry Ashurst’s total of 28 years, 9 months, and 7 days. Upon his retirement in 1969, Hayden had served in the Senate for 41 years and 9 months, and 30 days.
A statue of John C. Greenway, a Rough Rider and military officer, sculpted by Guzon Borglum, was unveiled in the U.S. Capitol as Arizona's first contribution to the National Statuary Hall Collection. In 2015 Arizona replaced Greenway's statue with one of Barry Goldwater.
President Franklin D. Roosevelt signed the Servicemen's Readjustment Act of 1944, better known as the "GI Bill." Originally proposed by Senator Ernest William McFarland of Florence and unanimously passed by both the House and Senate, the legislation helped returning veterans pay for education and housing to re-enter civilian life.
As chairman of the Joint Congressional Committee on Inaugural Ceremonies, Senator Carl Hayden accompanied President Harry Truman from the White House to the inaugural ceremonies at the Capitol.
Senate Democrats elected Ernest McFarland as their floor leader and Conference chairman and as the Democratic Policy Committee chairman. McFarland held these posts until 1953. He was defeated for reelection to the Senate in 1952 by Barry M. Goldwater of Phoenix.
Former senator Ernest McFarland was elected governor of Arizona and served from 1955 to 1959.
Senator Barry Goldwater published The Conscience of a Conservative, promoting a revival of conservatism.
Senator Barry Goldwater won the Republican Party nomination for president of the United States but was defeated in November by the incumbent president, Lyndon B. Johnson. Although Goldwater did not stand for reelection to the Senate that year, he returned to the Senate after winning election in 1968.
The Senate approved the "DeConcini Reservation" to the first of the Panama Canal Treaties. Offered by Senator Dennis DeConcini of Tucson, the provision authorized the use of military force "to reopen the Canal or restore operations to the Canal" if necessary, and helped secure sufficient support to win passage of the treaties.
Barry Goldwater became chairman of the Senate Select Committee on Intelligence, serving until 1985, when he became chairman of the Senate Committee on Armed Services . He chaired that committee until his retirement in 1987.
Senator Barry Goldwater received the Presidential Medal of Freedom, given by the president of the United States to honor individuals who have made great contributions to either the United States or the world. To date, 30 senators have received the award.
The Senate dedicated a portrait bust of former senator Carl Hayden, sculpted by Stafford Rolph. The bronze bust is located in the northwest corner of the Russell Senate Office Building, on the first floor, near the office that Senator Hayden had occupied for more than 20 years.
President Ronald Reagan signed the Goldwater-Nichols Act. Sponsored by Arizona senator Barry Goldwater and Alabama representative William Nichols, the act reorganized the Department of Defense and streamlined the military chain of command.
John McCain became chairman of the Senate Committee on Commerce, Science, and Transportation, serving until 2001, and again from 2003 to 2005.
Senator John McCain began a book tour in support of Faith of My Fathers, a biography that became a national best seller.
Senator John McCain won the Republican presidential primary in New Hampshire but lost the presidential nomination to George W. Bush later in the year.
Jon L. Kyl of Phoenix was elected chairman of the Senate Republican Policy Committee for the 108th Congress, a position he held until 2007, when he became Republican Conference chairman.
Kyrsten Sinema switched her political party affiliation from Democratic to Independent. While she received her seniority and committee assignments through the Democratic Conference for the purposes of organizing the Senate, she indicated she would not participate in either party caucus.