But by 1750, the Quakers were kind of on their way out; by 1750, they were a demographic minority in Pennsylvania, and by 1773 they were a minority in its legislature as well. In 1750 Quakerism was the third-largest religion in the US; by 1820 it was the ninth-largest, and by 1981 it was the sixty-sixth largest. What happened? The Quakers basically tolerated themselves out of existence. They were so welcoming to religious minorities and immigrants that all these groups took up shop in Pennsylvania and ended its status as a uniquely Quaker society. At the same time, the Quakers themselves became more “fanatical” and many dropped out of politics believing it to be too worldly a concern for them; this was obviously fatal to their political domination. The most famous Pennsylvanian statesman of the Revolutionary era, Benjamin Franklin, was not a Quaker at all but a first-generation immigrant from New England. Finally, Quakerism was naturally extra-susceptible to that thing where Christian denominations become indistinguishable from liberal modernity and fade into the secular background.

Source: Book Review of Albion's Seed by Slate Star Codex