James Logan - invented Conestoga wagon; Chief Justice of Pennsylvania Supreme Court; numerous other achievements
James Michener
Jane Adams
Joan Baez
Jocelyn Bell Burnell: discovered pulsars
John Dalton
John Greenleaf Whittier
John Woolman
Johns Hopkins
Joseph Lister
Joseph Lister, Sr. and Thomas Hodgkins, who together invented the compound microscope
Kathleen Lonsdale
Kersey Graves