( &&&&&&&&&&&01007.&&&&&0 1,007 km 2 ) State map highlighting Gilpin County Grand County 049 Hot Sulphur Springs 1874-02-02 Split from Summit County . Named for the Grand River which was renamed the Colorado River in 1921. &&&&&&&&&&013406.&&&&&0 13,406 &&&&&&&&&&&04839.460000 4,839.46 sq mi ( &&&&&&&&&&012534.&&&&&0 12,534 km 2 ) State map highlighting Grand County Gunnison County 051