Complex sentence: Freedom House, a nonprofit center of civil rights and advocacy for Boston's African American community, was founded in 1949 by the social workers (and married couple) Otto P. and Muriel S. Snowden.
Split into simpler sentences: Freedom House, was founded in 1949 as a center of civil rights and advocacy for Boston's African American community. The founders were the social workers (and married couple) Otto P. and Muriel S. Snowden.