McCauslen was born near Steubenville in the Northwest Territory (in what is now Ohio), and attended the public schools.
After he studied law, he was admitted to the bar and practiced in Steubenville.
McCauslen was commissioned on August 31, 1846, during the Mexican War as a captain and commissary of subsistence of the Third Regiment, Ohio Infantry.
He died in Steubenville, Ohio, March 13, 1863 and was interred in Union Cemetery.
This article incorporates public domain material from the Biographical Directory of the United States Congress