I found a link on the USPS site that list post offices for Washita County. While I do not think this is a complete list of every post office ever established in Washita County, it is still good to have the dates it does give.
Bessie – established 05/16/1895
Burns Flat – no dates given
Canute – est. 02/24/1899
Colony – est. 01/08/1896
Cordell – est. 10/12/1892
Corn – est. 04/27/1896
Dill City – no dates given
Foss – est. 09/15/1900
Herald – est. 11/30/1898 dis. 06/14/1902
Retrop – est. 01/12/1900 dis. 02/28/1905
Rocky – est. 07/12/1898
Sentinel – est. 10/13/1899
