His father was County Treasurer in 1855, and young Blackmore served as Chief Clerk.

Mayor Blackmore was engaged in the lumber and coal business.

The city expanded east and George Westinghouse began manufacturing the air brake in the Strip District during Mayor Blackmore's initial term.

His only child was called his name sake, James Blackmore Jr, it was unknown what he did for a living.

He died February 6, 1875, less than a week after finishing his term, and is buried in Allegheny Cemetery.