[1] Following the American entry into World War I, Greenwalt was commissioned into the United States Army as a second lieutenant.
[1] The following year, Greenwalt noted that many driver's licenses purchased in December were Christmas gifts.
[5] He ran for reelection as in 1940,[6] and served until 1941, when he was commissioned in the Iowa Army National Guard as a lieutenant colonel.
[11] By 1948, Greenwalt and his wife moved from West Des Moines, Iowa, to Fort Knox, Kentucky.
He died in Bradenton on September 28, 1979, and, following services on October 1, was buried in Arlington National Cemetery.