You are standing next to two brothels owned by the most successful Chinese madam in San Francisco, Ah Toy. She populated them with slave girls brought mainly from Canton. Due to the Chinese Exclusion act it was very difficult for free women to come and form regular families, and prostitution became one of the largest businesses in Chinatown.
Tongs bought or kidnapped girls and brought them over to San Francisco, where Ah Toy bought them. A girl who was between the ages of nine and twelve would be sold for $150 to $500, between twelve and sixteen from $500 to $1,500, while girls over the age sixteen were marketed for up to $3,500. The exact ownership of each slave was often a matter of much violent dispute between tongs. The girls life expectancy was approximately 5 years.
Turn around, and look across the street at the opposite end of the spectrum, the site of Belle Cora's brothel, one of the classiest establishments in early 1850s San Francisco, decorated with silks and damasks and offering music on pianoforte, harp and melodeon, which is probably why so many of the best citizens frequented it.
San Franciscans were always very music-loving people.