Serving as a Union Army captain during the American Civil War, he was captured and imprisoned in the notorious Confederate Libby Prison.

After the war, he became a prominent citizen of West Chester, Pennsylvania, and a partner in the law firm of William Darlington.

[1][2][3] When the American Civil War erupted in April 1861, Cornwell raised a company of infantry troops in response to President Abraham Lincoln's call for volunteers.

[1] At the Second Battle of Winchester in June 1863, Cornwell was captured by the Confederates while sick with typhoid fever in a military hospital.

In July 1864, he joined the staff of General James B. Ricketts, serving as provost marshal of the 3rd Division of the VI Corps.

A lifelong Republican who cast his first vote for president for John C. Frémont in 1856, Cornwell never sought elected office.

The couple had five children: Gibbons Gray, Martha Jackson, Mary Elizabeth, Ada Westlake, and William Darlington, who was named in honor of Cornwell's friend and business partner.