Thomas Barnum was the first elected sheriff. He was elected in May 1871 and resigned in November 1871. He was the cousin to PT Barnum and a forty year resident of Arizona. He helped build the north extension of the Swilling Canal.

Tom Barnum was the first elected sheriff of Maricopa County (his predecessor William Hancock was appointed to the post). When Barnum moved his family to the Salt River Valley in 1868, his wife was one of only four Anglo women in the rough settlement. Barnum was quick to see the Valley’s potential and went into partnership with J. W. Swilling in digging irrigation ditches. In 1871, when one candidate for sheriff shot and killed another candidate in a gunfight, Barnum became the front runner for the office. He was elected and served from May until November, 1871, when he resigned in order to devote his full attention to his ranch. He is said to have been a cousin of P.T. Barnum, the famous showman.

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