body of Lincoln and those of the three youngest of his sons were placed in crypts in the unfinished structure. In 1874, upon completion of the memorial, which had been designed by Larkin Goldsmith Mead, Lincoln's remains were interred in a marble sarcophagus in the center of a chamber known as the "catacombs," or burial room. In 1876, however, after two Chicago criminals failed in an attempt to steal Lincoln's body and hold it for ransom, the National Lincoln Monument Association hid it in another part of the memorial, first under wood and other debris and then buried in the ground within the tomb. When Mrs. Lincoln died in 1882, her remains were placed with those of Lincoln, but in 1887 both bodies were reburied in a brick vault beneath the floor of the burial room. By 1895, the year the State acquired the memorial, it had fallen into disrepair. During a rebuilding and restoration program from 1899–1901, all five caskets were moved to a nearby subterranean vault. Following completion of the restoration, State officials returned them to the burial room and placed that of Lincoln in the sarcophagus it had occupied in 1874–1876. Within a few months, however, at the request of Robert Todd Lincoln, the President's only surviving son, Lincoln's remains were moved to their final resting place – a concrete vault below the surface of the burial room. In 1930–31 the State reconstructed the interior of the memorial in an Art Deco style. Rededicated in the later year by President Herbert Hoover, it has undergone little change since that time. The Lincoln Tomb was designated a National Historic Landmark on December 19, 1960, and listed on the National Register of Historic Places on October 15, 1980. Design and layout The tomb is in the center of a 12½ acre (51,000 m²) plot. Constructed of granite from Biddeford, Maine, dressed at Quincy, Massachusetts, it has a rectangular base surmounted by a -high obelisk and a semicircular entranceway. A bronze reproduction by sculptor Gutzon Borglum of his head of Lincoln in the U.S. Capitol rests on a pedestal in front of the entranceway. Four flights of balustraded stairs—two flanking the entrance at the front and two at the rear—lead to a level terrace. The balustrade extends around the terrace to form a parapet. Originally open to the public, the terrace has since been closed due to safety concerns. In