Some may already know of this, but others may not...
If interested in what teams were kicking around in the 15 or so years before the 1871 National Association, start with this:
https://sabr.org/journal/article/185...ll-convention/
The complete list of pre-1900 Winter Meetings articles is here:
https://sabr.org/journals/winter-meetings-v3-1857-1900/
Great resource if you want to get some of the actual teams names, a few of the players and other key folks, and some of the loose organizations...