In 2010, journalist Rebecca Traister started a book that she thought would be about the twenty-first-century phenomenon of the American single woman. Over the course of her research, Traister made a startling discovery: historically, when women have had options beyond early heterosexual marriage, their resulting independence has provoked massive social change. Unmarried women were crucial to the abolition, suffrage, temperance, and labor movements; they created settlement houses and secondary education for women. Today, only 20% of Americans are wed by age 29, compared to nearly 60% in 1960. The Population Reference Bureau calls it a "dramatic reversal." Traister sets out to examine how this generation of independent women is changing the world.