McDowell was born in Trenton, Tennessee, and came to Montana in 1896.

In September 1933, McDowell was appointed to serve as minister to the Irish Free State by president Franklin D. Roosevelt;[3] he was reappointed in January 1934, as his initial appointment had occurred during a recess of the Senate.

[4] Upon presenting his credentials to Irish leaders on March 27, 1934, his official title was Envoy Extraordinary and Minister Plenipotentiary.

[4] Two weeks later, he died of a sudden heart attack on April 9, 1934, while attending a banquet in Dublin.

[6] After McDowell's death in Dublin several months later, his body was returned to the United States and he was buried in Memphis, Tennessee.