In 1956, the new Maine Medical Center building was opened, transforming the original Maine General Hospital complex into the largest medical facility north of Boston with a total of 420 hospital beds. Upon opening, 10,000 people toured the new wing, including MMC staff and Maine Governor, Edmund S. Muskie.

The hospital's main entrance was moved to the new wing and the Health Services division, which focused on preventive medicine, occupied the first floor. The Children's Hospital department was on the second floor, with Maine Eye and Ear Institute on the third. The fourth floor housed new labor and delivery rooms, nurseries and private rooms, and connecting to the pre-existing maternity unit.