Paul Freedman in DelanceyPlace:
In the mid-1800s, unaccompanied women in America were generally not allowed to dine at restaurants: "Midday dining presented a challenge for women too busy or too far from home to return there for lunch. They might be in the company of other women or alone, but at any rate not escorted by men who were occupied with work and work-related socializing; men had their own luncheon habits. In the nineteenth-century United States, men made the rules about public dining and admitted women to restaurants on sufferance, according to a complex series of arrangements. Different practices governed the two main meals of the day. "Restaurants depended economically on women accompanying men at the evening meal. Lunch, however, was segregated by gender and involved a series of problems, according to the social customs of the nineteenth century. In the grand and even not-so-grand metropolis, men were increasingly likely to work at some distance from home and to stay near their workplace for the midday meal. The point at which women too absented themselves from the house created a demand for their sustenance. The growth of cities and the creation of specialized shopping districts meant that it was often inconvenient for women as well as men to return home for lunch.
"The public rooms at fancy restaurants were usually reserved at lunch for men only, but some of them allowed women to have lunch in private dining spaces. In the era before Prohibition, bars offered free food, which, along with a crowded and boisterous atmosphere, encouraged demand for drink. Free-lunch bars were hopelessly inappropriate spaces for respectable women, as alcohol-driven conviviality was inevitably coarse — the antithesis of what was considered ladylike.