The adobe wall surrounding the plaza was replaced with a picket fence in 1881 and then a stone wall built by the Works Progress Administration in 1937. The WPA's walls and bandstand were unpopular and were removed just eleven years later through a grassroots effort organized by the Old Albuquerque Historical Society. The historical society also oversaw construction of a new bandstand, new landscaping, and installation of 16 wrought iron benches purchased from Chihuahua, Mexico. At the east end of the plaza is a display of two replica M1835 mountain howitzers. During the Civil War, retreating Confederate forces buried eight howitzers near the plaza in 1862 to prevent them from falling into Union hands. The guns were rediscovered in 1889 with the help of the former Confederate artillery commander, who still remembered their location. Two of the howitzers were put on display in the plaza but were later moved to the Albuquerque Museum of Art and History and replaced with replicas. At the west end of the plaza is a display of various flags which have flown over the city, including those of Spain, Mexico, and the United States. There was also a Confederate flag reflecting the brief occupation of the city by Confederate forces, but it was removed in 2015 amid the ongoing controversy surrounding such symbols. Most of the historic buildings in Old Town were built between 1870 and 1900, though some are older. Only one building, San Felipe de Neri Church, is proven to date to the Spanish colonial period. During the 20th century, many of the buildings were remodeled to facilitate modern commercial use, often including historically insensitive conversion of authentic vernacular and Victorian architectural details to a more idealized Territorial or Pueblo Revival style. Other buildings have been better preserved. Five properties in Old Town are listed on the National Register of Historic Places: