William J. Spencer

William J. Spencer (1867–1933) was an American labor leader who was secretary-treasurer of the Building Trades Department of the American Federation of Labor from its founding nearly continuously until his death in 1933.

Spencer was born in Hamilton, Ontario, in 1867. He became a plumber and emigrated to Buffalo, New York, in 1894, where he joined Local 36 of the Journeymen Plumbers.

Spencer was elected secretary-treasurer of the international Plumbers' union in 1897. In 1900, he was appointed "general organizer" of the union.

In 1903, Spencer was elected secretary-treasurer of the Structural Building Trades Alliance (SBTA). He served until 1908, when the SBTA affiliated with the American Federation of Labor (AFL) and became the Building Trades Department (BTD). He was elected secretary-treasurer of the BTD, and served until 1924. He was elected to the same office again in 1927, and served until his death in 1933.

In 1904, Spencer was elected eighth vice-president of the AFL. He served one year.

Spencer lived in Dayton, Ohio, from 1903 to 1912, after which he lived in Washington, D.C.