Harold Schworm Hacker was born in Buffalo, New York on July 9, 1916 to parents, Henrietta (Hank) Schworm and Joseph Hacker. Harold attended Canisius High School, a Jesuit-run institution for boys in Buffalo, New York and graduated in 1933. After graduation, he attended Canisius College where he earned a Bachelor of Arts in History in 1937. According to Hacker, he had dreams of becoming a history teacher but after a run-in with the college dean he decided to become a librarian. He received his Bachelor of Library Science from the University at Buffalo in 1941.

He began his library career as a page in 1934 at the Grosvenor Library in Buffalo. Here, he moved up the ladder as music librarian from 1940-1943 to Director of Public Relations from 1943-1947. Throughout his career Harold was very involved in local, regional, and national library organizations. He was active in the New York Library Association and the American Library Association. Hacker was well known throughout the library world and was sought after as a lecturer on the importance of communication in the in the library and applying business organizational practices to the libraries administrative structure. In 1947 Harold became the youngest president of the New York Library Association at the age of 30. In 1948 Hacker moved from the Grosvenor Library to become Deputy Director of the Erie County Public Library. He was deputy director until going back to the Grosvenor Library as Director in 1952. While Director, Harold implemented the first federated library system by merging the Grosvenor Library, Buffalo Public Library, and the Erie County Public Library to form the Buffalo and Erie County Public Library. Harold then moved to Rochester to become the Director of the Rochester Public Library. Hacker was Director of the Rochester Public Library from 1954-1978. He created the Pioneer Library System.

The Pioneer Library System consisted of libraries in the Monroe, Wayne, Ontario, Livingston, and Wyoming counties. The Pioneer Library System began in 1955 as the Tri-County Library System which included the Wayne County Public Library, Livingston County Public Library and the Monroe County Library System. In 1958 the Tri-County Library System changed its name to the Pioneer Library System but still only included the three original library systems. By 1960, the Pioneer Library System had added Ontario and Wyoming counties to the system. In 1989, the Monroe County Library System decided to break from the Pioneer Library System in order to have the federal grant money allocated separately.

Hacker was also involved, along with other regional librarians, in the formation of the Rochester Regional Research Library Council in March 1965 which was formed to improve collaboration between regional libraries. The RRRLC provided inter-library loans services, daily delivery services to participating libraries, reciprocal borrowing, continuing education, and a media center. The RRRLC was awarded its charter from the New York Board of Regents in 1966.

Aside from his impressive career as a librarian, Harold was an active volunteer with the community. He was involved in many organizations for the arts (including a weekly radio program called "Adventures in Jazz"), education, government, and social services. His largest contribution to the community was the many volunteer hours invested in bringing educational television programming to Rochester. Harold Hacker is widely acknowledged as the "Father of WXXI."

WXXI started as the Rochester Area Educational Television Association in 1958. From 1952-1958 RAETA produced educational programs for local schools. Hacker became the President of RAETA in 1962 and led the effort to obtain a broadcast license. When RAETA learned that a third VHF channel would be allowed in Rochester, Hacker spent countless hours fighting to secure the channel for educational television. Unfortunately, the bid for channel 13 was unsuccessful. RAETA and Hacker moved on to campaign for UHF channel 21. WXXI began airing programs on UHF channel 21 on September 6, 1966.

Hacker remained involved in the community well past his retirement from the Rochester Public Library in 1978. He spent his time giving speeches, writing, serving on a multitude of committees, and enjoying his very active social life, which included marrying the "light of his life" Joan Stein Smett at the age of 81.