According to the YMCA archives, 405 Carlton Avenue has some interesting history:
The Carlton Avenue branch of the Brooklyn Young Men's Christian Association was opened in 1902 under the leadership of executive secretary Charles H. Bullock, who had organized a branch for African-Americans in his native Charlottesville, Virginia. He was asked to come to Brooklyn to organize the first colored branch in Brooklyn, reflecting the national YMCA's growing interest in serving special populations such as immigrants, railroad workers, boys and African Americans. The work was funded by several well-known philanthropists, including George Foster Peabody, Julius Rosenwald, John D. Rockefeller, and members of the African-American community in Brooklyn. After starting its operations in a brownstone at 405 Carlton Avenue, in Fort Greene, the branch opened a typical YMCA building in 1918. The structure boasted 70 dormitory rooms, a swimming pool, bowling alleys, showers, meeting rooms, game rooms and a social lounge. It was, according to the Brooklyn Eagle, the second largest "colored YMCA" in the world. Women were welcome at this branch, and could participate in physical education classes designed for them. The branch was known for the prowess of its baseball team. In its early years, the branch focused on helping young men who had migrated from the south to New York, offering an employment service and other programs designed to help newcomers adjust to the city.
The branch closed in 1955, reflecting the decline in the need for a special branch for African Americans, who had moved away from the immediate neighborhood around the branch and were now served by other YMCA programs and buildings. The new residents of the neighborhood, many of whom had moved to New York from Puerto Rico, did not participate in YMCA programs. Moreover, the Carlton building was showing its age, and the Brooklyn and Queens YMCA was not eager to put money into a branch whose services might overlap with other branches close by. Finally, a controversy in the early 1950s over the firing of the executive secretary Herbert T. Miller, who had held the post since 1941, split the board and made cordial relations with the larger association difficult. As of 2012, the former YMCA building was operating as a nursing home.
Please find the original text at http://special.lib.umn.edu/findaid/html/ymca/ygny0025.phtml