[1][2] Rathbone's parents had been guests in the presidential box when Abraham Lincoln was assassinated on April 14, 1865.

The next year, his father murdered his mother and tried to kill himself, then was admitted to an asylum for the criminally insane in Hildesheim; Henry and his siblings were returned to the United States to be raised by their uncle, William Harris.

He was a delegate to the Republican National Convention in 1916 which nominated Charles Evans Hughes for the presidency.

He was elected as a Republican to the United States House of Representatives in 1922, and served from 1923 until his death in 1928.

Rathbone also served one year as President of the Illinois State Society of Washington, DC, until his death.