Harlow was born in Newburyport, Massachusetts. He began his working life as a journalist, before becoming manager of Walter Hagen, then the biggest draw in golf, in 1921. In 1930, he was hired as tournaments manager by the PGA of America and he played a key role in establishing a full-time PGA Tour. (The precise date this happened is a matter of interpretation, but money lists are available from 1934 onwards.)
Harlow was a born salesman who went from city to city persuading local clubs and businesses to support or create tournaments. He introduced ideas such as a year-round schedule, the tournament volunteer system and the PGA's merchandise show. He kept the show on the road through the Great Depression. He also managed players such as Paul Runyan, Horton Smith and Ed Dudley. In 1936, he was replaced as tournament manager by Fred Corcoran as the PGA felt he had a conflict of interest, acting as agent for certain players while he was running a tour which was expected to treat all its members equally. He went on to found Golf World magazine in 1947. In 1988, he was inducted into the World Golf Hall of Fame.