Recently I have been working in an old membership record book for the Middle Tennessee Conference of the Southern States Mission. The book doesn't have a lot of explanatory notes, but appears to cover from about 1888 to 1920. There are a few entries from prior to 1888, but the entries are few and far between, and only for people who had stayed in Tennessee and stayed in the Church.
This was about the period when members were no longer being encouraged to gather, whether that be to Utah, Colorado, or Texas. There was still some emigration, but for the most part people were staying where they lived, unless they needed to move for better employment.
The map below shows entries in the book, specifically baptisms, in the County listed as the members postal address. In some cases, this was not where the person was baptized, but where they lived between 1888 and 1920. In most cases, people stayed where they were. There is some fluidity which makes the graphic less precise, but when taken as a whole it isn't too bad of an indicator of both membership and baptism.
Note that East Tennessee is under represented. There was at the time a separate conference for East Tennessee, and a separate membership book. The line dividing the two changed frequently. The few records I have for east Tennessee counties were baptized in Middle Tennessee but subsequently moved to East Tennessee.
I know you can't read the county names, but there are three counties (in red) that stand out as high baptizing areas. Lawrence County - in the center bottom - had been the focus of Church activity after 1884 and led the Conference with 111 baptisms in 32 years. Shelby County (Memphis) followed next with 96 baptisms in the same period. Perry County - in the center - came in third with 87. Shelby County is the only urban center among them, and was virtually ignored by the Church until 1900.
My next plan is to look at this over time, perhaps add East Tennessee, and baptisms from other sources prior to 1888.