( &&&&&&&&&&&04959.&&&&&0 4,959 km 2 ) State map highlighting Custer County Delta County 029 Delta 1883-02-11 Split from Gunnison County . Named for the town of Delta located at the delta of the Uncompahgre River . &&&&&&&&&&030401.&&&&&0 30,401 &&&&&&&&&&&02977.&50000 2,977.05 sq mi ( &&&&&&&&&&&07711.&&&&&0 7,711 km 2 ) State map highlighting Delta County Denver County