|As an extremely old city, Philadelphia has more than its fair share of ghosts.
Sin-Eaters haven't shunned the area, either. There's no real organization locally (or most anywhere for Sin-Eaters), just a loose collection of krewes and individuals. Many of the local Sin-Eaters over history have attached themselves to motleys, cadres, and coteries.
Philadelphia has many smaller gates, including one in the graveyard at Mikveh Israel)but the most well-known and largest runs underneath Hood Cemetery. Specifically, it opens next to the grave of Christian Frederic Post. A missionary from Prussia, Post's first and second wives were both Lenape, and his ability to speak multiple languages made him central to diplomatic efforts during the French and Indian War which preserved the nascent city of Pittsburgh.
The guardian of the gate is a hooded and masked individual of indeterminate gender; the mask appears differently depending on the viewer. It refers to itself with no name, and local Sin-Eaters refer to it euphemistically as "Our Friend." Who knows, maybe it was a Quaker, or maybe it's a little like when the Fae are referred to as the 'Fair Folk.'