Well, the entry says that Cumberland was an American Post. So I did more research into this and looking at old maps of that period. In Maryland, currently, is a town called Cumberland. In researching that town's history, it was once called Ft Cumberland and was in existence during your Rundell's time. Maryland was one of the first 13 states. Records from 1788 and before does exists, but you may have to get creative in what records you look at.