[2] Clark was born in Germantown, Philadelphia, Pennsylvania, on November 30, 1861, to a family of bankers and financiers.

[3] As a student at Harvard University, Joseph Clark won the U.S. intercollegiate singles and doubles titles in its inaugural staging, in the spring of 1883.

He and his brother, Percy Hamilton Clark, opened a law practice at 321 Chestnut Street in Philadelphia.

The practice centered on the "street railway, electric light, and power businesses" operated by E. W. Clark & Co.[5] In 1885, he took the U.S. National lawn tennis doubles title, and also became champion of Canada, the first American to be so.

Clark was also a semi-finalist at the U.S. National Championships lawn tennis singles in 1885, 1886, the same year he also won men's Mosseley Challenge Cup at the Bar Harbor Open, and 1887.