Mixon took over command of the unit -- and the entire Army base -- during a morning ceremony at Manhart Parade Field on the post near Colorado Springs.
Mixon told those gathered for the change-of-command that, "we must now press on to win the victory that so many have suffered and died to achieve."
He replaces Major General Robert Wilson, who had been commander since October 2002.
Mixon was previously the chief of staff at the Army Futures Center at Fort Monroe, Virginia.
Wilson will become assistant deputy chief of staff for Army operations in Washington, D.C.