When Justice Robert C. Grier retired from the U.S. Supreme Court, Strong was suggested as a possible replacement. However, President Ulysses S. Grant was heavily lobbied to nominate former Secretary of War Edwin Stanton. Stanton was nominated, and confirmed by the United States Senate, but he died just four days later without having served on the Court. Grant then nominated Strong on February 7, 1870, who was confirmed without a recorded vote and was sworn in on March 14, 1870. Strong ruled for states rights and against the Civil Rights Act of 1866, which had allowed African Americans to testify against Whites, in Bylew v. United States.