The Women's Bureau, within the Department of Labor, was created in 1920 in order to "improve the status of wage-earning women, improve their working conditions, increase their efficiency, and advance their opportunities for profitable employment," according to the bureau mission statement.
While much of the information offered by the bureau covers recent trends and developments in women's employment, the very existence of the bureau and the period in which it was founded speaks to the history of women's rights in the U.S. As such, the statistics offered can serve as a an extension to units on women's suffrage and increasing roles outside of the domestic sphere. Take a look at how the bureau's history reflects changing labor concerns of the 20th and 21st centuries.
A great place to start is the bureau's quick facts and reports. The quick facts, lists of relevant statistical data, include the 20 most common women's occupations as of 2008 and data on female RNs (registered nurses). Also take a look at the data book, Women in the Labor Force.
Women's history is a great way to discuss many of the events of the 20th century (early amendments, WWII, etc.) through a traditionally overlooked historical perspective.