The acronym “T.E.R.F.”—trans-exclusionary radical feminist—is variously a slur or a badge of pride, depending on your views. And Britain, where I live, has for some years been known as “T.E.R.F. Island.” On my side of the pond, gender-critical feminists have racked up a series of political victories, but their American sisters seem, by contrast, few and fragmented. This has long puzzled me. Why are so many British feminists critical of gender ideology, while their American counterparts seem monolithically in favor? Two recently published books, offering complementary histories of American second-wave feminism from the sexual revolution to the present, shed light on this strange phenomenon.