The first post office in Elk County (Howard County) was Elk River. It was on the upper reaches of the Elk in the northwest of the county in what would later be Union Centre township. I have never been able to find anything about this place except that it appears on an early inaccurate map of Howard County.
The post office at Elk River was established in 1868.
On October 30, 1869, the Post Office in Washington DC, advertised for bids to deliver mail to post offices, among many others, as follows:
From Oswego by Big Hill, Salt Springs, Elk River, and Douglas to Wichita 125 miles and back once a week. Leave Oswego Monday at 6 am; arrive at Wichita Wednesday by 7pm. Leave Wichita Thursday at 6 am, arrive at Oswego Saturday by 7pm.
The second post office established in Elk County (Howard County) was Howard City in February 1870.