Pittsburgh, Pennsylvania, long has been a stronghold of the Presbyterian Church, as has western Pennsylvania in general.

The troubles of the national denomination over issues such as recognition of same-sex practice are affecting congregations withing the Presbyterian heartland.
This article from the Pittsburgh Tribune-Review online:

The congregation of the largest church in the Pittsburgh Presbytery voted overwhelmingly Sunday to split with the national church and join a smaller, more conservative Presbyterian denomination.

The Mainline Denominations continue their move to the sideline.