Clark Lockwood was born in 1846 in Starkey, Yates County, New York to Robert Lockwood (1818 - 1864) and Jane (Clark) Lockwood (1821 - 1912). Clark's parents were married in 1845. In 1850 the family was living in Starkey, with Robert (33) listed as a "Farmer" in the census. Jane's age is given as 29, and the childrens' as Clark (4), Elizabeth (2) and Hesther A. (4 months). Also living with the family is William C. Price (5). By the time of the 1855 New York state census the family had relocated to Dix, Schuyler County, New York, and youngest daugther Jane A. Lockwood had been born. Robert's father James Clark (68) was living with the family, as was a 17-year-old servant, Elizabeth Gandy[?]. In the 1860 census at Dix the family is listed as Robert (41), Jane (39), Clark (13), Libbie (11), Hester (9), Jennie (7). Living with the family were Parmelia Gardner (18), "Dress Maker"; Kate Cayle (15), "Domestic"; George Dickens (30), "Farm Labour"; and Henry Wyant (39), "Livery Labour."

Clark Lockwood enlisted as a private in Company B of the 17th New York Cavalry on August 14, 1863 at Elmira, New York. The regiment was never entirely formed, however; those who had enlisted were transferred to the 1st New York Veteran's Cavalry. Lockwood served until being mustered out on July 20, 1865 at Camp Piatt, West Virginia. A muster roll abstract describes him as "student, black eyes, dark hair, dark complexion, 5 feet 5 1/2 inches high." In June 1864 he was detailed to detached service at Martinsburg, West Virginia, and in October 1864 he was serving as clerk at the regimental headquarters in Charleston, West Virginia.

By the time of the 1865 New York state census the widowed Jane Lockwood was keeping a boarding house in Dix, with eleven boarders besides her children: Clark (19), Libbie (17), Esther (15) and Jane (13). In 1870 they had relocated to Watkins, where the census finds Jane (49), Clark (24), Libby (22), Esther A. (20) and Jennie (18). Clark's occuption is given as "Book Keeper." In the 1880 and 1900 censuses Jane is living alone; in 1910, aged 89, she lives with the family of her daugther Elizabeth, who had married Emmett B. Russell. Jane died on May 8, 1912.

In the 1880 census Clark Lockwood (34) was living several houses down from his mother in Watkins, with his occupation given as "R.R. Baggage & Express"). In July 1890 he applied for an invalid's pension, which was reapplied for by his mother in September 1897. In the 1890 Veterans Schedules his enlistment term is given as September 8, 1863 to July 21, 1865. Clark Lockwood died on February 18, 1897 in Watkins Glen.

Robert, Jane, Clark and other members of the Lockwood family are buried in Glenwood Cemetery, Watkins Glen, Schuyler County, New York.