Frederick Thomas Fairfax Johnson was born on November 30, 1864 in Hagerstown, Maryland, 10 days after his father died.

His father, Thomas S. J. Johnson, served with the 1st Regiment Maryland Volunteers. He enlisted on May 27, 1861 as a Captain. He was commissioned a Lt. Colonel after being captured on May 31, 1864 at Cold Harbor, Virginia. Thomas died on November 20, 1864 of disease while a prisoner in Charleston, South Carolina.

Frederick joined Lincoln Camp 2, Washington D.C., in 1889 and was elected Commander of the Maryland Division in 1902. Before becoming Commander-in-Chief, he served the National organization as Judge Advocate General (1900) and National Counselor (1908).

He was a graduate of the National Law School in Washington D.C and became a retail lawyer and patent attorney.

He was a member of the Sons of the American Revolution, Maryland State Society, and Maryland Historical Society.

In 1904, he married Isabella Wilson and they had no children.

Brother Johnson died on May 11, 1928 and is buried in Loudon Park Cemetery in Baltimore, Maryland. His pallbearers were Past Department Commanders of Maryland and Lieut. Col. U. S. Grant 3rd.