(http://i941.photobucket.com/albums/ad256/waldoegray/45th%20inf_zpsegemeevj.png)
This is the shoulder patch of the 45th US Army Infantry Division formed in 1924. The division was head quartered in Oklahoma City and was composed of National Guard units in Arizona, Colorado, New Mexico, and Oklahoma.
The unit fought in WWII and Korea and was one of the first units called up in WWII.
In 1939, the shoulder patch was changed.
(http://i941.photobucket.com/albums/ad256/waldoegray/45th%20pre%201939_zpszdczx25o.png)