He attended the College of Wooster in Wooster, Ohio. He graduated from the college of law of Ohio State University at Columbus, Ohio, in 1925.
He was admitted to the bar the same year and commenced practice in Piqua, Ohio. He served in the United States Army from December 26, 1943, to October 12, 1945. McCulloch was elected as a Republican to the Eightieth Congress, by special election, on November 4, 1947 to fill the vacancy caused by the resignation of Robert Franklin Jones.
He was re-elected to twelve consecutive Congresses.
He introduced civil rights legislation months before Kennedy presented his act to congress. This was politically imprudent, considered by some to be even political suicide.
Representative McCulloch had only a few of African-American constituents and so few votes to gain from introducing or supporting civil rights legislation. had been distressed when then Senate Majority Leader Johnson watered down civil rights bills in 1957 and 1960 to make them practically unenforceable. Throughout his career, McCulloch was a conservative (demonstrated by low Americans for Democratic Action (American Dental Association) scores) despite his strong support of civil rights.
As ranking Republican on the House Judiciary Committee, he, with Democratic Chairman Emanuel Celler, pushed the Civil Rights Acting of 1964 through the House of Representatives.
During the Great Society Congress, he opposed most Great Society legislation. After the Great Society Congress (1965–1966), he began to adopt a few liberal positions, such as supporting strong gun control legislation in 1968 a well as busing. He was not a candidate for reelection in the 1972 election to the Ninety-third Congress.
He resumed the practice of law in Piqua, Ohio, and died in Washington, District of Columbia, on February 22, 1980.
Interment in Arlington National Cemetery. In early 2010, McCulloch was proposed by the Ohio Historical Society as a finalist in a statewide vote for inclusion in Statuary Hall at the United States Capitol.
McCulloch"s influence with the Civil Rights Acting led President John Kennedy to declare, "Without him it can"t be done." McCulloch was recognized by Kennedy"s successor, Lyndon Johnson, under whom the act was passed, as "the most important and powerful political force" in passing the Acting. Todd Purdum, in his history of the civil rights era An Idea Whose Time Has Come, said in an interview:.
He was a member of the Ohio House of Representatives from 1933 to 1944, serving as minority leader from 1936 to 1939 and as speaker from 1939 to 1944. As the ranking member of the House of Representatives Judiciary Committee, William McCulloch took a leading role in the civil rights movement. McCulloch was the ranking minority member of the House judiciary committee, and he told the Kennedy Administration that he would back a strong bill in the House – and urge his fellow Republicans to follow suit – but only if the White House agreed not to trade away the bill"s strongest provisions in the Senate, and also agreed to give Republicans equal cr for passing lieutenant
Married Mabel Pauline Harris, November 8, 1926. Children: Nancy Jane, Adah Annual.