Born in Maryland, Johnson came west in 1808, venturing into the vast Louisiana Territory recently acquired from Spain.
He situated at a spot near the junction of the Des Moines and Mississippi rivers, at the site of what is now known as Keokuk, Iowa.
At the end of the War of 1812, he supervised distribution of $30,000 in gifts from the United States to 19 Native American tribes, who signed the peace agreements at Portage Des Sioux, Missouri.
Following a mayoral election in April 1833, the apparent winner, Dr. Samuel Merry, was ruled ineligible due to his concurrent holding of a U.S. federal office.
[3] While working as indian agent at Prairie du Chien, Johnson married Tapissee, the daughter of the Sauk Chief Keokuk.