He was born in 1845 in Clarksburg, Virginia (now West Virginia), son of Lloyd Lowndes and Elizabeth Moore; he was a great-grandson of early Bladensburg, Maryland settler, Christopher Lowndes (1713–1785). He attended Allegheny College in Pennsylvania, where he was a member of Phi Kappa Psi fraternity. He graduated from the law department of the University of Pennsylvania at Philadelphia in 1867.
