He was a member of the influential Van Leer family and his ancestors were some the earliest settlers of the Pennsylvania Colony.

At the outbreak of the Civil War Van Leer joined the Union Army at Gloucester City, New Jersey with his family, and was commissioned as a Captain, promoted to Major and Lieutenant colonel of the 6th New Jersey Volunteer Infantry in 1861.

[3][4] Van Leer's regiment was the first fully equipped brigade to arrive in Washington, D.C. just before the First Battle of Bull Run.

[5] After his regiment built Fort Runyon, Van Leer lead 10 companies during Hooker's Virginia campaigns.

[14] Van Leer built and leased houses for free black tradesmen and to people who were supportive of the free black community in Lima, Pennsylvania at a location now known as Van Leer Avenue.