Kelly's Station was in Allegheny Twp on the Allegheny River quite some distance from Apollo. (BTW, there is no Apollo Twp., but Apollo is adjacent to Kiskiminetas Twp.) The postoffice at Kelly's Station seviced most of southern Armstrong Co at one time.
About that time (1870) is when Allegheny Twp, which included most of SW Armstrong Co, was split into Gilpin Twp, Bethel Twp, and Parks Twp. Kelly's Station ended up in Bethel Twp.
Here is a link to an 1970 Armstrong County map.http://www.pa-roots.com/~armstrong/maps/ArmstrongCo.jpg
Kelly's Station is shown on the Allegheny River. This map also indicates that Apollo was also a PO for that area in 1870.
Here is a link to a more modern map on the same website. Just click on the proper twp on the county map.http://www.pa-roots.com/~armstrong/maps/index.html
BTW, the Allegheny Twp link does not seem to work anymore.