His older brother Daniel, a local attorney, moved to eastern Ohio in 1826, settling in Carrollton.

Not long afterward, John McCook also moved to the Buckeye State and established a practice in New Lisbon and later in Steubenville.

He served as a volunteer surgeon in the Union Army during the Civil War.

[2] He died just after its close at the headquarters of his son, General Anson G. McCook, in Washington, D.C., during a visit.

[1][3] McCook was buried at Union Cemetery in Steubenville beside his wife, who had preceded him in death by just seven months.