Pierce was an assistant United States attorney in New York from 1953 to 1955. A lifelong Republican, he first entered government when Eisenhower was president. He became an assistant to the Undersecretary of Labor in 1955. Pierce was appointed by Governor Nelson Rockefeller to serve as a judge in New York City, 1959–1960. Pierce was named a partner of the law firm of Battle Fowler in 1961, the first African-American partner of a major New York firm, and was there until 1981 except for a period from 1970 through 1973 when—during the Nixon presidency—he was general counsel for the Department of the Treasury. Pierce argued before the United States Supreme Court on behalf of Martin Luther King Jr. and the New York Times in the important First Amendment case styled New York Times v. Sullivan. In 1981, Pierce became Secretary of Housing and Urban Development under Ronald Reagan. Pierce was Reagan's only African American cabinet member and the only cabinet member to serve in his post throughout both of Reagan's terms as President. On June 18, 1981 during a luncheon for the US Conference of Mayors in Washington DC, President Reagan mistook Pierce for one of the mayors on the dais, with the famous "Hello, Mr. Mayor" comment. Due to his perceived low profile within the Reagan administration, he was sometimes derided as "Silent Sam." During Pierce's tenure, HUD appropriations for low-income housing were cut by nearly half and funding all but ended for new housing construction.
Political scandal
After leaving office, he was investigated by the United States Office of the Independent Counsel and the United States Congress over mismanagement, abuse and political favoritism that took place in the department during his tenure. These investigations found that under Pierce's stewardship the department engaged in political favoritism and trading of influence. Millions of dollars of federal government money was given to projects sought by connected politicians of both parties, in violation of rules governing such grants and expenditures. Through the 1990s many of Pierce's closest aides and confidants at the department were charged and convicted on felony charges related to the political favoritism and inappropriate expenditures that pervaded the department during Pierce's tenure. Pierce himself was not charged, however.
Death
Pierce died at the Holy Cross Hospital outside Washington, D.C., on October 31, 2000, at the age of 78.