CLINTON (Missoula) is an old mining and lumber town. Ore deposits were discovered in 1889 and the Charcoal Mine yielded thousands of dollars worth of lead and silver. The name Clinton was chosen that year in honor of Henry Clinton. Originally the place had been known as Betters' Station. It was started as a stage station on the Mullan Road in 1883 and named for Austin Betters, a homesteader. The Northern Pacific railroad men first called this place Wallace, but the name was unacceptable to the Post Office Department. At different times the settlement was also called Pine Grove (which was very descriptive) and Blossberg. The Clinton post office, with Samuel Scott in charge, opened in 1892.The book does not have footnotes, so I don't know where Cheney found this information, and she passed away in 2005, so I cannot ask her. She did, however, include a bibliography, so there are six pages of published and unpublished sources that I can hunt down and look through to find her source.
One of the many cool things that you will find at the Bozeman Public Library is a bunch of historic maps of Montana hanging on the walls upstairs. Yesterday I made a point to look at each one, record the date, and write down what town names were listed in the Hellgate Valley between Missoula and Drummond. The 1887 map from the U.S. General Land Office and the 1888 map from George F. Cramer both identify the town where Clinton now stands as "Wallace." Every newer map (from 1895 on) calls the town "Clinton." The older maps did not identify any town in that area. This corroborates the dates and names given by Cheney in her book.
I only had time to thoroughly examine one other book before the library closed. That was Montana Post Offices and Postmasters by Dennis J. Lutz. While that book corroborated the facts about Clinton's post office contained in Cheney's book, it omitted the fact that the post office had existed prior to that. Its name changed from "Wallace" to "Clinton" in 1892. The Wallace post office was actually established on May 7, 1883, with Elias Bryan as postmaster. According to Lutz's book, Austin Betters' wife (and my great-great-grandmother), Jane Betters, served as postmaster from December 24, 1890 (Christmas Eve) until May 7, 1892, when the name changed to Clinton and Samuel Scott became postmaster.
Jane Better's granddaughter, Mable A. Terry, also served as postmaster at the Clinton post office. Her term was from April 17, 1945 to December 1, 1957. An Edith M. Terry also served as postmaster from March 5, 1921 to December 4, 1923, but I am unsure of her relation to the Betters family.
Incidentally, all of the facts contained in Lutz's book (and more) are actually available online at the U.S. Postal Service's website, as I just discovered (It doesn't allow direct links to search results, so you'll have to go to http://webpmt.usps.gov/pmt002.cfm and enter "Clinton" and "Montana" in the search boxes to see this). I'm not sure how I didn't come across that before. I suppose it's all in the way you search for things online.
In summary, the earliest mention of Betters' Station that I have found so far is 1971 (Cheney), and if people were calling present-day Clinton "Betters' Station" in the 1880s, it doesn't appear that it was the postal service.