When the Territorial Government building opened in 1901, the city of Phoenix had 5,500 people. When Arizona was declared a state in 1912, the population had doubled. Its slowest decade of growth was the 1980s at 24.5%. During the 1950s, the increase was over 300%. No wonder the three branches of Arizona’s government outgrew their original statehouse. In 1960, the Capital Mall became a triad of buildings. The Senate and this House of Representatives building face each other with the historic Arizona State Capitol in the middle.