The Old Post Office Pavilion is located at 230 S. Fifth Street, in El Centro, California. It was originally constructed to house the U.S. Post Office in El Centro. Built between 1933 and 1934, the building was one of the last Beaux Arts-style public structures in the United States, and housed postal operations until late in 1985, when it was acquired by the City. 

The building was listed on the National Register of Historic Places on March 13, 1985. It remains the only Imperial County building so named on this registry.

Steps in the 1993-34 construction period were documented in photographs taken by well-known Imperial County photographer Leo Hetzel. Among Hetzel's photos (part of the collection at Imperial Valley College): 

	1) Laying the cornerstone (dated 1932), January 10, 1933.
	2) Dedication grandstand, January 10, 1933.
	3) Excavation of earth for basement construction, February 1, 1933.
	4) Basement sidewall construction, February 20, 1933.
	5) Reinforced steel for the building's first floor, March 13, 1933.
	6) Steel framing viewed from the south on Olive Avenue, April 29, 1933.
	7) Rear parking area viewed from the northwest, December 30, 1933.
	8) Completion of exterior as viewed from Olive Avenue, December 30, 1933.
	9) Terra cotta work, as approved in Washington, D.C., March 13, 1933.
	10) Ornamental grill work, as approved in Washington, July 17, 1933.

The Old Post Office Pavilion was refurbished by the City of El Centro using funds from the California Office of Historic Preservation. For a time, it served as the home of the Imperial County Arts Council.

According to City Manager Ruben Duran, during the summer of 2006, the City will be bidding out work to remodel the OPOP. This will include painting the exterior and interior, reconstruction of the handicapped access ramp, minor roof repair, repair of interior lighting, reconstruction of the stage, remodeling the kitchen and replacing the seats in the balcony. Earlier this year the heating and air conditioning units were replaced. "The challenge for the refurbishing is finding time when the building is not being used for theater productions," Duran says.

The building operation is under the management of the El Centro Parks and Recreation Department with overview from the Community Services Commission. The Imperial Valley Arts Council is no longer in the building due to a reorganization of the council. The Mostly Theater Company, a not-for-profit organization, hold their productions in the OPOP. This month the production is "Steel Magnolias". During the past year there have been several productions including a sold-out series for "Sound of Music." This summer MTC has planned two children's productions.