John Calvin McCoy, lawyer and politician, son of John and Jane (Collins) McCoy, was born on September 28, 1819, in Clark County, Indiana. He was educated at Clark County Seminary and Wilmington Seminary. After Clark County Seminary closed in 1837, he worked as deputy circuit clerk of Clark County until 1839. While thus employed he studied law in his spare time. Subsequently he was employed in Missouri, first as a surveyor and later as an Indian agent. In the spring of 1840 he returned to Indiana to study law. In May 1841 he received his license to practice. McCoy moved to Dallas in the spring of 1845 as surveyor and subagent for the Peters colony. Although he severed his connection with the company in June 1846, he remained a citizen of Dallas for the remainder of his life. He was the first active lawyer to settle in Dallas and was generally considered the founder of the Dallas Bar Association. He played an active role in the organization of Dallas County and was elected its first district clerk in July 1846. He resigned in December of that year to return to his law practice. In 1851 he married Cora M. McDermot (McDermett). In July 1853 McCoy's wife and only child died and were buried on the same day. He never remarried.
In 1856 he was elected district attorney of the Sixteenth Judicial District, a position he held for nearly three years. During the early months of the Civil War he was assigned to duty as mustering officer for the Confederate regiments raised by Nathaniel M. Burford and Trezevant C. Hawpe. Afterward he served as provost marshal for Dallas County. In 1862 he was elected to represent Dallas County in the Texas House of Representatives. He was reelected in 1864 and served until the Hamilton government was inaugurated under presidential Reconstruction. After the war McCoy remained active in Democratic party politics and was highly regarded as a speaker, although he was never again a candidate for elective office. In addition to his political activities, he consistently maintained a highly successful law practice, which, with his real estate investments, made him one of the wealthiest men in the county. He was a founder and one of the first members of the first Masonic body in Dallas, Tannehill Lodge. He was elected to state office in the Masonic order on numerous occasions. He belonged to the Dallas County Agricultural and Mechanical Society and served at one time as corresponding secretary. When a Texas Historical Society was founded in Houston in 1870, McCoy was elected one of the vice presidents. He was a founder and the first president of the Dallas County Pioneers Association, organized in 1875. In October 1880 he joined the First Baptist Church of Dallas, and he remained active in that church for the remainder of his life. At the time of his death he was president of the Dallas Public Library Association. He died on April 30, 1887. McCoy's philanthropy in general and his particular love for children of all classes and races were widely recognized in Dallas. After his death, his body lay in state for four days at his home, where, according to the Dallas Morning News, "hundreds and hundreds of his old neighbors, of his newer friends, the rich and the poor, the black and the white...visited." The burial service at the Masonic Cemetery was attended by a crowd that the Dallas Morning News estimated in the thousands.