We're all used to calling the Watch Tower Bible and Tract Society of Pennsylvania by the abbreviations WTBTS or WTS, but in a recent JWdotORG article, they consistently refer to the original Pennsylvania corporation as WTPA.
WTBTS aka WTPA
There are two Watchtower corporations. The Pennsylvania based corporation is their headquarters for legal issues.
In the US there is 8 main corporations used by Watchtower.
truth_b_known and AbusedandPissed:
Yes, there are a number of secondary corporations like the WTS of NY, Florida, Canada, Christian Congregation of JWs, etc. But what we're talking about here is the main original one: WTS of Pennsylvania that Russell started. It isn't just used for legal issues, it holds the copyright to nearly ALL publications, owns loads of property and much more.