Originally known as "Salt River Dam #1", it was not until 1959 that the dam and reservoir were officially named after Theodore Roosevelt. It was the largest masonry dam in the world for its time with a height of 280 feet (84 m) and a length of 723 feet (216 m).

In 1894 Fenn J. Hart became the first mayor of Tempe. He served until April 20, 1896, after which he continued to serve on the Tempe Town Council until 1900.

When the Mexican-American War ended in 1848, Mexico ceded its northern zone to the United States, and the region's residents became U.S. citizens. The Tempe area became part of the New Mexico Territory. On February 24, 1863, during the Civil War, Congress passed the "Arizona Organic Act", which split off the western portion of the 12-year-old New Mexico Territory as the new Arizona Territory.