I'm your huckleberry.
Roughly a quarter of my ancestry is German, coming from both of my grandmothers and much of it from those who settled in Pennsylvania.
It may be helpful to you to know how it breaks down as my guess is you are likely looking for Pennsylvania Dutch ancestry.
My paternal grandmother's family came from 3 main German lines. The most recent line (Reuter, Ost, Uphoff) immigrated to Philadelphia in the mid-19th century and were Catholic from Bundenbach and Birkenfeld region (former Duchy of Oldenburg, now RP), St. Wendel/Morbach Saarland region and Emsdetten in Württemberg.
Another line (Bender, Fridburg) immigrated to colonial Philadelphia in the early 18th century. They came from the Kraichgau region in Germany.
These two lines appear to be very diverse in their stock... intermarriage not so great as to be considered endogamous.
But then there's the Pennsylvanian Dutch line (Yon, Brown, Höh, Dickensheets, etc.). These ancestors came over in the 17th century and settled in Fredrick County, MD/Adams County, PA, Bedford, Blair and Huntingdon Counties, PA. Many of them were German Anabaptist (Brethren) and, until the later 19th century, married within their small communities keeping the gene pool rather endogamous. They also came from a region in Germany (Landstuhl, Zweibrücken) whose population was highly endogamous (more on that below.)
My maternal grandmother's mother was 100% German and while her parents (who were first cousins) brought their family over in the late 19th century and settled in Illinois, they came from the very same villages and shared the same surnames as are common among Pennsylvania Dutch (Kettenring, Höh, Hollinger, Biehl, Zimmer, Trautmann, etc.). They just happened to arrive in the US 150 years or so later. But they were still incredibly, incredibly endogamous.
So much so that I can't believe I haven't yet matched up with anyone through those lines...however my one Jewish grandparent's even more endogamous genes seem to be skewing my DNA match results.
My GEDmatch ID: T498657. And my full GEDCOM (8412103) is also uploaded as well : ) Hope it helps!