DETROIT (AP) ― Diego Rivera’s murals at the Detroit Institute of Arts have been designated as one of four new national historic landmarks.

Federal officials announced the designation on Wednesday.

The Detroit Industry murals were conceived by Rivera as a tribute to the city’s manufacturing base and labor force of the 1930s. The Mexican artist in 1932 and 1933 completed the murals on walls of a court in the museum and they’re considered to be among his greatest works.

The largely symbolic landmark designation comes amid efforts to protect the collection of the Detroit Institute of Arts from being sold as part of the city’s bankruptcy.

The National Historic Landmarks Program offers technical assistance, recognition and funding for landmarks, but doesn’t shield from ownership changes.