Johns Hopkins was born in Anne Arundel County, Maryland, the second of eleven children, on a 500 acre tobacco plantation. When his Quaker parents freed their slaves in 1807, Johns and his brother were put to work in the fields, interrupting their formal education. Johns worked for a time in his uncle's wholesale grocery business, where he fell in love with his cousin Elizabeth. Hopkins couldn't marry Elizabeth because her parents wouldn't allow it, since prejudice against first cousins marrying was strong among Quakers. Both of them agreed never to marry.
Hopkins and Jonathan Moore, also a Quaker, went into business together. The business later became Hopkins & Brothers after Moore dissolved the partnership claiming that Johns loved money too much, after which Hopkins partnered with his three brothers. Hopkins & Brothers sold various wares in the Shenandoah Valley from wagons in exchange for corn whiskey which was then sold in Baltimore as "Hopkins' Best". Later Hopkins invested heavily in the Baltimore and Ohio Railroad, which is where he made most of his fortune. He twice put up his own money to bail out the railroad in 1857 and 1873.
When Hopkins died in 1873 with no heirs (having never married) he left $7 million (mostly in B&O stock) to found the world-famous Johns Hopkins University and Johns Hopkins Hospital in Baltimore, Maryland, as was indicated in his 1867 will. At the time it was the single largest philanthropic donation ever.
People often mistakenly assume that his forename was "John" (much to the annoyance of alumni of the University and other informed persons). His forename is from a family surname. His great-grandmother, Margaret Johns, married Gerard Hopkins, and who named their son Johns Hopkins, whose name was passed on to his grandson.