The document explores the historical trends in female labor force participation (FLFP) among married women in the United States from 1860 to 2010, noting a U-shaped relationship between FLFP and economic development. It discusses various factors influencing FLFP, including social customs, education, and the occupational status of husbands. The study utilizes extensive census data and hierarchical modeling to analyze regional variations and suggests that while certain mechanisms behind the U-shape are valid, there is insufficient evidence for a definitive U-shaped trend on a national level.