Clara Maass Medical Center is a hospital in Belleville, Essex County, New Jersey, United States, that is part of the Barnabas Health. It was founded in 1868 as the Newark German Hospital, and was renamed in 1952 in honor of Clara Maass, a former nurse who trained there at the hospital's Christina Trefz Training School for Nurses, and become the hospital's head nurse. Maass' 1901 death during yellow fever experiments attracted national attention.