Question: Robert Nelson Cornelius Nix Sr., was an American politician who served in the United States House of Representatives from 1958 until 1979, he was the first African American to represent Pennsylvania in the House of Representatives, the first African Americans to serve in the United States Congress were Republicans, elected during which time period?

Context articles: African Americans in the United States Congress
Donald Andrew Spencer, Sr.
Robert N. C. Nix Jr.
John Patterson Green
Jefferson F. Long
List of African-American United States Senators
Robert N. C. Nix Sr.
K. Leroy Irvis
Richard E. Jackson
Nix Federal Building

The first African Americans to serve in the United States Congress were Republicans elected during the Reconstruction Era.
 After slaves were emancipated and granted citizenship rights, freedmen gained political representation in the Southern United States for the first time.
 White Democrats regained political power in state legislatures across the South and worked to restore white supremacy.
 By the presidential election of 1876, only three state legislatures were not controlled by white Democrats.
 The Compromise of 1877 completed the period of Redemption by white Democratic Southerners, with the withdrawal of federal troops from the South.
 State legislatures began to pass Jim Crow laws to establish racial segregation and restrict labor rights, movement and organizing by blacks.
 They passed some laws to restrict voter registration, aimed at suppressing the black vote.
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.
Robert Nelson Cornelius Nix Jr. (July 13, 1928 – August 23, 2003) served as the Chief Justice of the Pennsylvania Supreme Court from 1984 to 1996.
 Nix was the first African-American Chief Justice of any state’s highest court, and the first African American to be elected to statewide office in Pennsylvania.
 He served as a justice of the Supreme Court of Pennsylvania for 24 years, 12 of which were as chief justice, and was a prominent figure in Pennsylvania law and public service for more than three decades.
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.
Jefferson Franklin Long (March 3, 1836 – February 4, 1901) was an American politician from Georgia.
 He was the second African American sworn into the US House of Representatives, and the only African American to represent Georgia until Andrew Young was elected in 1972.
 Long was the first African American to speak on the floor of the US House, opposing the Amnesty Bill that exempted former confederate serving in the House from swearing allegiance to the Constitution.
The United States Senate has had ten African-American elected or appointed office holders.
 The United States Senate is the upper house of the bicameral United States Congress, which is the legislative branch of the federal government of the United States.
 The US Census Bureau defines African Americans as citizens or residents of the United States who have origins in any of the black populations of Africa.
 The term is generally used for Americans with at least partial ancestry in any of the original peoples of sub-Saharan Africa.
 During the founding of the federal government, African Americans were consigned to a status of second-class citizenship or enslaved.
 No African American served in federal elective office before the ratification in 1870 of the Fifteenth Amendment to the United States Constitution.
 The Fifteenth Amendment prohibits the federal and state governments from denying any citizen the right to vote because of that citizen's race, color, or previous condition of servitude.
 Of the ten senators, six were popularly elected (including one that previously had been appointed by his state's governor), two were elected by the state legislature prior to the ratification of the Seventeenth Amendment to the United States Constitution in 1913 (which provides for the direct election of U.S. Senators by the people of each state), and two were appointed by a state Governor.
 The 113th United States Congress (2013–15) marked the first time that two African Americans served concurrently in the Senate.
Robert Nelson Cornelius Nix Sr. (August 9, 1898 – June 22, 1987) was an American politician who served in the United States House of Representatives from 1958 until 1979.
 He was the first African American to represent Pennsylvania in the House of Representatives.
 The Robert N. C. Nix Federal Building in Philadelphia, Pennsylvania is named in his honor.
K. Leroy Irvis (December 27, 1919 – March 16, 2006) was a teacher, activist and politician based in Pennsylvania; he was the first African American to serve as a speaker of the house in any state legislature in the United States since Reconstruction.
 (John Roy Lynch (1847–1939) of Mississippi had been the first African American to hold that position.)
 Irvis, a Democrat, represented Pittsburgh in the Pennsylvania House of Representatives from 1958–1988.
Richard Ernest Jackson Jr. (born July 18, 1945) is an American politician and mathematics teacher.
 He made black history in 1984 when he became Mayor of the City of Peekskill.
 Peekskill was the first city in all of New York State to have an African American Mayor, making Jackson - as reported by both the New York Times .
 and Ebony Magazine.
 - New York State's first African American Mayor.
 In 1974, the Village of Bridgewater (population 574) laid some claim that their Village elected an African American Mayor, Everett T. Holmes, prior to Mayor Jackson's appointment.
 Everett served as mayor from 1974-1976 and from 1979 until his death in 1982.
 However, the village of Cleveland in Oswego County can claim the first African American to be elected its chief executive.
 Edward "Ned" Sherman was elected in a special election in May, 1878 to fill the unexpired term of the chief executive, called President of the village, who quit a month after being elected.
The Robert N. C. Nix Sr.
 Federal Building and United States Post Office, formerly known as the United States Court House and Post Office Building, is a historic building in Philadelphia, Pennsylvania.
 Built in 1937–1941, it was designed by Harry Sternfeld in the Moderne style and features several sculptures and reliefs by Donald De Lue and Edmond Amateis.
 It was renamed in December 1985 in honor of Robert N.C. Nix Sr., a longtime Democratic Congressman from Pennsylvania's 1st Congressional District in Philadelphia, and the first African-American to represent Pennsylvania in Congress.