Prince Hall Masonry, which was formed while Masonry in the United States was effectively segregated on racial grounds, has a predominantly black membership. Various philosophical and technical reasons historically prevented US "mainstream" Grand Lodges from recognising or acknowledging Prince Hall Grand Lodges as "regular bodies" operating in accordance with the Landmarks of Freemasonry. Originally having one Grand Lodge for the whole United States, separate Prince Hall Grand Lodges now operate in most US states and jurisdictions. Many PHGLs also sponsor and govern Prince Hall Lodges abroad, principally on or near US military bases. Since the early 1990s onward, most, but not all, US Grand Lodges and Prince Hall Grand Lodges began to extend mutual recognition and promote visitations and fellowship between their members.