When Peoria, Arizona, was settled in the late 1800s, one of the key players was a man named William J. Murphy. He
helped develop the area by setting up businesses, the most valuable of which was the Arizona Canal Company.
That brought water to the area and allowed for agricultural, encouraging more migration here.
Murphy helped set up a Post Office in the new communiity in 1888 and named it Peoria, an homage to his former home town, Peoria, Illinois. That was the name of the town when it incorporated on June 4, 1888.