John M. Dean, early Presidio county attorney and land speculator, son of Dr. Y. S. and Martha (McCullough) Dean, was born in Forsythe County, Georgia, on May 13, 1852. When he was seven the family moved to North Carolina. During the Civil War Y. S. Dean served as a surgeon in Gen. Robert E. Lee's command. By 1874 John Dean was in Lee County, Texas, where he was admitted to the state bar. In 1878 he moved to Fort Davis, then in Presidio County. Since he had no money to open a law office, he drove an Overland stagecoach from Fort Davis to Van Horn Wells for three months.
In May 1878 Dean began his law practice in Fort Davis. He was appointed Presidio county attorney in 1879 but resigned a few months later. He was elected county attorney in 1880 and resigned in May 1882 to enter the cattle business with James B. Gillett and C. L. Nevill. In 1882 Dean was elected district attorney of the Twentieth Judicial District, a post to which he was reelected for 1884–90 and 1896–1902. From 1892 until 1896 he served a four-year term as state senator. From 1902 to 1909 he practiced law privately. Dean caused a controversy when he made Marfa the Presidio county seat without legal authority. In 1884 he bought the land around the Marfa railroad siding from the Galveston, Houston and San Antonio Railway Company. On October 9, 1885, he conveyed part of the section to four prominent citizens who supported making Marfa county seat. Dean and his four allies managed an election to legalize the action.
Dean was a Mason. He married Louise Haggart, and they lived first in Marfa. The couple moved to El Paso in 1889. Dean lived just over ten of his fifty-seven years in Presidio County. He died on August 20, 1909, in Chicago, Illinois, and was buried in El Paso. Fifty members of the bar and fifteen Chinese friends gathered on the Dean lawn during the Masonic funeral to pay him tribute.