Occupying the White House after Theodore Roosevelt - Wilson took office in March 1913, Roosevelt left in March 1909, with Taft serving a term in between - Wilson sought to undo the Republican Roosevelt's integration. In fact, Wilson would not only undo Roosevelt's appointments of Blacks to federal offices, but Wilson would also go on to undo the integration of the federal civil service which had been in place since Reconstruction. Wilson imposed segregation on various agencies within the government, e.g. the post office, which had been integrated for decades.
Beyond removing African-Americans from federal posts, and beyond re-segregating the civil service, Wilson went further. He publicly praised the KKK. This horrified not only Blacks, but millions of Americans - people of all races, religions, and ethnic background. His affirmation of the Ku Klux Klan was the final bit of evidence which confirmed that Woodrow Wilson was a hate-filled and bigoted racist.
Just as Wilson had worked to undo the desegregation of Teddy Roosevelt and William Taft, so Wilson's successors - Harding, Coolidge, and Hoover - worked to reintroduce integration to the federal government and civil rights to the Blacks. Harding and Coolidge both advanced a legislative agenda which included antilynching bills. Hoover worked to reintegrate federal agencies. Historian Jonathan Bean writes:
In 1913, Democratic president Woodrow Wilson ordered the segregation of government offices. Moorfield Storey and other officers of the NAACP protested, but Wilson responded: "[B]y putting certain bureaus and sections of the service in the charge of negroes we are rendering them more safe in their possession of office and less likely to be discriminated against." Perhaps because he had spent most of his adult life outside the United States, Secretary of Commerce Hoover was uninterested in racial issues; moreover, thinking in terms of rigid classes violated his individualist philosophy. Hoover's Red Cross work during the Great Flood of 1927 opened his eyes to racism in the South. The following year he responded positively when the NAACP asked him to desegregate the Commerce Department.
The narrative, then, is this: on the state level, the civil rights gained by the Blacks during Reconstruction began to evaporate during the late 1800's, as Democrats regained control of southern states from the Republicans. On the federal level, the civil rights gained by African-Americans during Reconstruction began to evaporate during the Democrat administration of Woodrow Wilson; Blacks began to regain ground on the federal level during the Republican administrations of Harding, Coolidge, and Hoover. African-Americans would have to wait longer to regain that ground on the state level, as the Democrat party held the southern states under racist domination even when the Republicans had influence on a federal level.