[1][2] His parents, Robert Ryland Sizer, a lumber industry executive, and Mary T. Thomsen, were married in 1890.
[1] In World War II, he served in the Monuments, Fine Arts, and Archives program as a lieutenant colonel.
For his work, he was awarded the Order of the Crown of Italy with rank of Commander from the Italian government in 1945.
[1][2] He designed a new flag for the city of St. Louis, Missouri that was officially adopted on February 3, 1964.
[2][10] Sizer published over 160 items, especially about the life and works of the American artist John Trumbull.