Question: What type of structure does North Carolina Granite Corporation Quarry Complex and United States Bullion Depositor have in common?

Context paragraphs:
Granite Quarry School: Granite Quarry School, also known as Schuford Memorial Elementary School and Granite Quarry Elementary School, is a historic school complex located at Granite Quarry, Rowan County, North Carolina.  The main school building was built in 1933, and is a one-story, "H"-shaped building sheathed in granite.  It has a side gable roof with shed dormers and a pedimented entrance portico.  Connected to the main building by open, covered walkways are the cafeteria (1956) designed by Leslie Boney and a classroom building (1960).  It was originally built for African-American students and continued to operate until 1968 when its students were integrated into other county schools.

United States Post Office (Iowa Falls, Iowa): The United States Post Office is an historic building located in downtown Iowa Falls, Iowa, United States.  Built in 1914, the structure was designed in the Neoclassical style, with Oscar Wenderoth as the supervising architect.  The 1893 Colombian Exposition in Chicago was a major influence in the building's design.  The foundation is composed of North Carolina granite, while the walls are dark red brick that is laid in an English cross bond.  The main entrance is framed by a portico that is held up by four columns of the Doric order.  The interior features woodwork of white oak, a marble-terrazo floor, and a vaulted ceiling.  It was listed on the National Register of Historic Places in 1994.

North Carolina Granite Corporation Quarry Complex: North Carolina Granite Corporation Quarry Complex is a historic granite quarry and national historic district located at Mount Airy, Surry County, North Carolina.  The district encompasses 22 contributing buildings, 1 contributing site, and 8 contributing structures in an area approximately one mile long and 1/3 mile wide.  Notable contributing resources include the cutting shed (1927), the office building (1928), and a building originally used as a blacksmith shop.  It is the world's largest open faced granite quarry.  Granite from the quarry was used to build the United States Bullion Depository at Fort Knox, the Arlington Memorial Bridge in Washington, the Wright Brothers National Memorial at Kitty Hawk, and the Albert Einstein Memorial in Washington.

Francis Osborne (North Carolina politician): Francis “Frank” Osborne (1853-1920) was the Attorney General of North Carolina from 1893-1896.  Osborne was born in Charlotte, North Carolina and attended the University of Virginia before reading law for 2 years in the offices of Richmond Mumford Pearson, Chief Justice of the North Carolina Supreme Court.  Osborne was admitted to the North Carolina Bar in 1875.  At age 25, he was elected mayor of the city of Charlotte.  He was elected Attorney General of North Carolina in 1893, but, defeated for reelection to the same office in 1896.  Osborne served a term as a State Senator from Mecklenburg County, North Carolina in the North Carolina General Assembly from 1898-1899.  He served on 9 standing Senate Committees.  After 1899, Osborne resumed his legal practice at the law firm of Osborne, Maxwell & Kearn.  Though, himself, a Democrat, in 1901 Osborne defended both North Carolina Supreme Court Chief Justice David M. Furches and North Carolina Supreme Court Associate Justice Robert Martin Douglas during their impeachment hearings.  Osborne was of the opinion that the Republican judges’ impeachments were unwarranted and an attempted political purge.  Osborne’s brilliant speech before the North Carolina General Assembly in closing defense of the justices caused both to be acquitted.  As reward for his successful defense of the justices, Theodore Roosevelt upon assuming office as President of the United States appointed Osborne a United States District Judge.

Camden Confederate Monument: The Camden Confederate Monument, also known as the Confederate Women's Memorial, is located on the grounds of the Ouachita County Courthouse in Camden, Arkansas.  The sculpture, carved out of Italian marble, depicts a woman dressed in the period of the American Civil War, standing with her feet together, clutching a flagpole.  The sculpture is mounted on a block of North Carolina granite, next to a tall (28 ft ) obelisk.  The statue is 5 ft tall.  The obelisk is inscribed on three sides, recognizing the valor of women in the Confederate cause, and the organizations that funded the memorial's construction.  The memorial was erected in 1914 by the local chapters of the United Confederate Veterans and the United Daughters of the Confederacy.

Fort Knox: Fort Knox is a United States Army post in Kentucky south of Louisville and north of Elizabethtown.  It is also the site of the United States Bullion Depository, which is used to house a large portion of the United States' official gold reserves.  The 109,000 acre (170 sq mi, 441 km²) base covers parts of Bullitt, Hardin, and Meade counties.  It currently holds the Army Human Resources Center of Excellence to include the Army Human Resources Command, United States Army Cadet Command and the United States Army Accessions Command.

Flat Rock, Surry County, North Carolina: Flat Rock is a census-designated place (CDP) in Surry County, North Carolina, United States.  The name "Flat Rock" stems from the community's granite quarry.  The granite quarry is the largest open-face granite quarry in the world, and has been mined continuously since 1889 by the North Carolina Granite Corporation.  Flat Rock's best known resident is Ricky Bowman.

Frank I. Osborne: Francis "Frank" Irwin Osborne (1853–1920) was the Attorney General of North Carolina from 1893 to 1896.  Osborne was born in Charlotte, North Carolina and attended the University of Virginia before reading law for 2 years in the offices of Richmond Mumford Pearson, Chief Justice of the North Carolina Supreme Court.  Osborne was admitted to the North Carolina Bar in 1875.  At age 25, he was elected mayor of Charlotte, North Carolina and served in the office from 1879-1880.  He was elected Attorney General of North Carolina in 1893, but, defeated for reelection to the same office in 1896.  Osborne served a term as a state senator from Mecklenburg County, North Carolina in the North Carolina General Assembly from 1898-1899.  He served on 9 standing Senate Committees.  After 1899, Osborne resumed his legal practice at the law firm of Osborne, Maxwell & Kearn.  Though, himself, a Democrat, in 1901 Osborne defended both North Carolina Supreme Court Chief Justice David M. Furches and North Carolina Supreme Court Associate Justice Robert Martin Douglas during their impeachment hearings.  Osborne was of the opinion that the Republican judges’ impeachments were unwarranted and an attempted political purge.  Osborne’s brilliant speech before the North Carolina General Assembly in closing defense of the justices caused both to be acquitted.  As reward for his successful defense of the justices, Theodore Roosevelt in the same year appointed Osborne an associate justice of the United States Court of Private Land Claims.

United States Bullion Depository: The United States Bullion Depository, often known as Fort Knox, is a fortified vault building located within the United States Army post of Fort Knox, Kentucky.  The vault is used to store a large portion of United States official gold reserves and occasionally other precious items belonging or entrusted to the federal government.  It is estimated to hold roughly 2.3% of all the gold ever refined throughout human history.

Granite Railway: The Granite Railway was one of the first railroads in the United States, built to carry granite from Quincy, Massachusetts to a dock on the Neponset River in Milton.  From there boats carried the heavy stone to Charlestown for construction of the Bunker Hill Monument.  The Granite Railway is popularly termed the first commercial railroad in the United States, as it was the first chartered railway to evolve into a common carrier without an intervening closure.  The last active quarry closed in 1963; in 1985, the Metropolitan District Commission purchased 22 acre , including Granite Railway Quarry, as the Quincy Quarries Reservation.

Supporting paragraphs: North Carolina Granite Corporation Quarry Complex United States Bullion Depository
Answer: building