The Lincoln Tomb is the final resting place of the 16th President of the United States, Abraham Lincoln, his wife, Mary Todd Lincoln, and three of their four sons, Edward, William, and Thomas. Constructed about 1860, the vault is at the base of a hill north of the Tomb. The Lincoln Tomb was designated a National Historic Landmark in 1960; it was placed on the National Register of Historic Places in 1966. The Tomb is operated by the Illinois Historic Preservation Agency. The Tomb, designed by sculptor Larkin Mead, is constructed of brick sheathed with Quincy granite. The base is 72 feet square with large semi-circular projections on the north and south sides. Double sets of stairs lead to a terrace, above which rises the 117-foot-tall obelisk. At the corners of the shaft, large pedestals serve as bases for four bronze sculpture groups, each representing one of the four Civil War military services—infantry, artillery, cavalry, and navy. A taller base on the obelisk’s south side holds a heroic bronze statue of Lincoln. In front of the Tomb is a bronze reproduction of Gutzon Borglum’s marble head of Lincoln, which is displayed in the U.S. Capitol in Washington, D.C. Interior rooms of the Tomb are finished in highly polished marble trimmed with bronze. The south entrance opens into a rotunda, where hallways lead to the burial chamber. The rotunda and corridors contain reduced-scale versions of important Lincoln statues, as well as plaques with excerpts from Lincoln’s farewell address to Springfield, the Gettysburg Address, and his Second Inaugural Address. President Lincoln’s remains rest in a concrete vault ten feet below the marble floor of the burial chamber. A massive granite cenotaph marking the gravesite is flanked by the presidential flag and the flags of states in which Lincoln's ancestors and Abraham Lincoln himself resided. Crypts in the chamber’s south wall hold the remains of Mary, Edward, Willie and Tad Lincoln. The remains of President Lincoln and his son Willie were placed in the receiving vault from May 4 through December 21, 1865. From December 21, 1865 through September 19, 1871, the remains of the President and two of his sons, Eddie and Willie, were moved into a temporary above-ground tomb constructed on the northeast side of the hill where the current tomb now stands. Tad Lincoln, the President’s youngest son, died on July 15, 1871. His remains were the first to be interred in today’s Tomb, followed by those of his father and his two brothers on September 19, 1871. Mary Lincoln died at her sister's home in Springfield on July 16, 1882. She was laid to rest with her martyred husband and dear sons a few days later. Construction of the Lincoln Monument began in 1868. It was dedicated in 1874 in a ceremony attended by President U.S. Grant. Due to design and construction faults, the Tomb was extensively rebuilt in 1900-01 and again in 1930-31. Because of security concerns (thieves attempted to steal Lincoln’s body in 1876), President Lincoln’s remains were moved to their final resting place, below the floor of the burial chamber, after the first renovation. The second reconstruction also involved a complete redesign of the interior of the tomb, including creation of the inside corridors, installation of the marble and bronze ornamentation, and addition of the small statues. The Borglum bust outside the Tomb was installed at the same time.