From the Summary: "In total, 162 African Americans have served in Congress. This total includes  152 African Americans (146 Representatives and 6 Delegates) elected only to the House of Representatives;  9 African Americans elected or appointed only to the Senate; and  1 African American who has served in both chambers. The first African American Members, Senator Hiram Revels of Mississippi and Representative Joseph Rainey of South Carolina, both took the oath of office in 1870. These first two Members were among the 22 African American Members (2 in the Senate, 20 in the House) who began their service in the period of time after the Civil War but prior to the start of the 20th century. After these first 22, the presence of African Americans in the membership of Congress was not continuous, and there were subsequent periods in both chambers with no African American Members. Most recently, the 116th Congress began with the highest number of African American Members ever at the start of a Congress: 57 (52 Representatives, 2 Delegates, and 3 Senators)."
CRS Report for Congress, RL30378
Congressional Research Service: https://crsreports.congress.gov/