Mixed-sex education
Coeducation is the American English term for integrated education of men and women. Before coeducation became predominant, most important institutions of higher education restricted their enrollment to men. Women were educated in all-female schools, if at all.
Coeducation in the United States
The first coeducational institution of higher education in the United States was Oberlin College in Oberlin, Ohio. The agitation for coeducation by feminists grew through the American Civil War era, and by 1872 there were 97 American universities admitting women. Some institutions refused to integrate fully, but were willing to educate women in closely associated schools--a variation on the later "separate but equal" standard of racially segregated schools followed in some parts of the US. Examples of this parallelism include Radcliffe College at Harvard University in Massachusetts and Barnard College at Columbia University in New York. A variety of gender-segrated women's institutions were founded, notably the Seven Sisters of New England. Some of these "girls schools" are now coeducational (e.g. Vassar), others are not (e.g. Wellesley).
It should be noted that many or most "common schools"--the neighborhood, village and county schools that educated most Americans through the end of the 19th century--were coeducational from the beginning, in part because small school districts could not fund separate educational facilities for girls and boys.
Remarkably, after a little more than than a century in the mainstream higher education system of the United States, American women now earn the majority of bachelor's degrees and account for 60% of the enrolled undergraduate population.