Arizonans were clamoring for statehood by the early 20th century. After rejecting a 1906 congressional decision that Arizona and New Mexico enter the Union as a single state, Arizonans took political matters into their own hands. In 1910, they elected 52 delegates (41 Democrats and 11 Republicans) to a state constitutional convention. Many of the representatives—who included Arizona’s first governor, George W.P. Hunt, and Barry Goldwater’s grandfather—had progressive, populist leanings.

They drew up one of the nation’s most liberal state constitutions, with provisions meant to give greater political voice to average Arizonans, including voter initiatives, referendums, and recalls. President William Howard Taft, who thought recalling judges would compromise judicial independence, threatened to veto Arizona’s admission unless the provision was removed. It was, and Arizona was granted statehood. Voters, however, had the last laugh when they passed a constitutional amendment in the state’s first general election in November 1912 that restored the controversial measure. It was Wild West democracy in action.

The Western landscape also created problems. Snowmelt and rain regularly sent the Salt River over its banks. Luckily, President Theodore Roosevelt was ready to ride to the rescue with a bold plan and several million dollars. Roosevelt tasked the newly formed federal Bureau of Reclamation with building a hydroelectric dam on the Salt River in 1911 to control flooding and generate electricity. It was the first project the new agency tackled, and the Roosevelt Dam tamed the free-flowing river by diverting the whole flow from its banks into an expanded canal system, leading to one of the city’s first big boom periods. With an economy fueled by the “Five C’s”—citrus, cotton, cattle, copper, and climate—Phoenix’s population mushroomed to nearly 30,000 people by 1920, then added almost 20,000 more by 1930, matching the Hohokam’s previous record of 50,000 inhabitants in just 50 years.

The state came of age during World War II with the bombing of the USS Arizona at Pearl Harbor. The Sonoran Desert’s terrain was an ideal spot for training soldiers to fight in the deserts of North Africa, and thanks to the state’s blue skies and open stretches of land, new airfields were constructed, 60 in all by the end of the war. Moreover, the large, land-locked state also provided space for 23 prisoner-of-war camps, which were scattered around Arizona, including one at Phoenix’s Papago Park, the site of the largest mass escape of POWs in the United States during the war. When they weren’t escaping, the German POWs helped with projects like canal maintenance and harvesting cotton crops. Also, due to the state’s proximity to large Japanese-American populations in California, several Japanese relocation and work camps were built, including one just south of Phoenix on the Pima–Maricopa Indian reservation.

During this time, one of the most important pieces of legislation in American history was drafted by an Arizona senator, Ernest W. McFarland. The World War I veteran, having witnessed the poverty many servicemen were forced to endure after returning home, fought to pass a bill that granted tens of thousand of veterans financial assistance for education and housing. As the primary sponsor of the GI Bill, McFarland was a major force behind its unanimous passage in the Senate and House, although it’s unlikely he anticipated the sweeping effects it would have on the nation when President Franklin D. Roosevelt signed the bill into law in 1944. McFarland eventually served in the state’s three highest offices: U.S. senator, governor, and chief justice of the Arizona Supreme Court.