Question: Which National Historic Landmark in Oberlin, Ohio was also home to the first African American that was elected to a United States Public Office? 

Context paragraphs:
Maggie L. Walker National Historic Site: The Maggie L. Walker National Historic Site is a United States National Historic Landmark and a National Historic Site located at 110½ E. Leigh Street on "Quality Row" in the Jackson Ward neighborhood of Richmond, Virginia.  The site was designated a U.S. National Historic Landmark in 1975.  The National Historic Site was established in 1978 to tell the story of the life and work of Maggie L. Walker (1867-1934), the first woman to serve as president of a bank in the United States.  It was built by George W. Boyd, father of physician, Sarah Garland Boyd Jones.  The historic site protects the restored and originally furnished home of Walker.  Tours of the home are offered by National Park Service rangers.

Charles Young Buffalo Soldiers National Monument: The Colonel Charles Young house is a National Historic Landmark in Wilberforce, Ohio.  A career U.S. Army officer, Charles Young was born into slavery in Kentucky in 1864.  He was the third African American graduate of West Point, the first black U.S. national park superintendent, the first African American military attaché, and the highest ranking black officer in the United States Army until his death in 1922.  He also taught military science at Wilberforce University.

Tappan Square: Tappan Square is a public park and National Historic Landmark at the center of Oberlin, Ohio.  The park initially opened in 1885, on 13 acre of city-owned land at the bequest of Oberlin College benefactor Charles Martin Hall.  It was designed by the esteemed duo of Frederick Law Olmsted, Jr. and John Charles Olmsted.  The square in Oberlin was named in the 1940s, in honor of Arthur and Lewis Tappan, wealthy merchants of New York City who supported Oberlin College in its early days and who were ardent abolitionists.  The square was previously known as College Park or the Campus.  Until 1965 it held the Historic Elm, under which John Jay Shipherd and Philo Stewart were said to have knelt and prayed to God and on which spot they decided to found the town.  The square held college buildings for many years, including a five-story brick college classroom and men’s dormitory called Tappan Hall.  As the buildings on the square grew older, the area was cleaned up as a green space for the community, in accordance with the provisions of the will of Charles Martin Hall.

Guthrie Historic District (Guthrie, Oklahoma): The Guthrie Historic District (GHD) is a National Historic Landmark District encompassing the commercial core of Guthrie, Oklahoma, US.  According to its National Historic Landmark Nomination it is roughly bounded by Oklahoma Avenue on the north, Broad Street on the east, Harrison Avenue on the south, and the railroad tracks on the west; it also includes 301 W. Harrison Avenue.  The National Historic Landmarks Program on-line document describes the boundaries as "14th Street, College Avenue, Pine Street and Lincoln Avenue.  One building, the Logan County Courthouse, is at 301 E. Harrison Avenue, outside the main boundaries of the GHD," This article relies on the former source, which is more detailed.  According to the 1998 nomination, the proposed district covered 31 acres .  The nomination included 112 resources, classed as 69 contributing buildings, 38 non-contributing buildings, 1 non-contributing structure and 3 noncontributing objects.  It was declared a National Historic Landmark in 1999 for its historic significance as the first capital of the Oklahoma Territory and of Oklahoma.

San Juan Bautista State Historic Park: San Juan Bautista Plaza Historic District, also known as San Juan Bautista State Historic Park is a historic district in San Juan Bautista, California, United States, that is a National Historic Landmark and a California state historic park.  It includes the Mission San Juan Bautista, the Jose Castro House (another National Historic Landmark), and several other buildings.  It became a State Park in 1933 and was declared a National Historic Landmark in 1970.

National Historic Landmark: A National Historic Landmark (NHL) is a building, district, object, site, or structure that is officially recognized by the United States government for its outstanding historical significance.  Of over 90,000 places listed on the country's National Register of Historic Places, only some 2,500 are recognized as National Historic Landmarks.

Donald Andrew Spencer, Sr.: Donald Andrew Spencer, Sr. (March 5, 1915 – May 4, 2010) was one of the first African American realtors in Cincinnati, the first African American broker to join the Cincinnati Board of Realtors, the first African American broker to serve as President of the Cincinnati Board of Realtors, and also the first African American trustee at Ohio University in Athens, Ohio.  He was appointed trustee of Ohio University by former Ohio Governor John J. Gilligan.  He was the first African American to chair the Ohio University board of trustees in 1979 and served on the Ohio University board from 1974 to 1983.  He was also the founder of the Beta Eta Chapter of Kappa Alpha Psi, a predominantly African American fraternity, at the University of Cincinnati.  He founded the chapter in 1939.

John Patterson Green: John Patterson Green (April 2, 1845 – September 1, 1940) was an American attorney, politician, public servant and writer.  He was among the first African Americans to hold public office in Cleveland, Ohio after he was elected as the Republican Justice of the Peace in 1873.  He served as a member of the Ohio House of Representatives, and in 1891, he was elected to the Ohio Senate becoming the first African American Senator in the state serving from 1892 to 1893.  Green is remembered for introducing the legislation that established Labor Day in Ohio as a state holiday.

List of U.S. National Historic Landmarks by state: The United States National Historic Landmark Program is designed to recognize and honor the nation's cultural and historical heritage.  The program was formally inaugurated with a series of listings on October 9, 1960; as of February 16, 2017, there are 2,596 designated landmarks.  A National Historic Landmark (NHL) is generally a building, district, object, site, or structure, that is officially recognized by the United States government for its national historical significance.  A National Historic Landmark District (NHLD) is a historic district that is recognized as an NHL.  Its geographic area may include contributing properties that are buildings, structures, sites or objects, and it may include non-contributing properties.

John Mercer Langston House: The John Mercer Langston House is a National Historic Landmark in Oberlin, Ohio.  It was home to John Mercer Langston, attorney, abolitionist, diplomat, US Congressman and college president, who as town clerk in Oberlin was one of the first African Americans elected to public office in the United States.

Supporting paragraphs: John Mercer Langston House National Historic Landmark
Answer: John Mercer Langston House