Colonel John Johnston was born in Ireland and immigrated to the United States when he was 11 years old.

Johnston settled in Pennsylvania and stayed there until he entered the mercantile trade. During this time, Johnston transported goods to various forts across the frontier.

Johnston later became a Federal Indian Agent in Fort Wayne, Indiana prior to taking the same position in Piqua, Ohio. In this role, Johnston operated a trading post and acted as a peacekeeper during the War of 1812.

As an Ohio Canal Commissioner, he was also instrumental in the construction of the canal system in Ohio.

Johnston was a prominent Mason in both Philadelphia and Piqua. He was buried with military and Masonic honors in the Johnston family cemetery on February 23, 1861.