He began his working career as a grocer in Philadelphia and became a business tycoon with financial interests in oil, natural gas and transportation.

He partnered with Peter Widener to found the Philadelphia Rapid Transit Company and developed streetcar and railway systems throughout several major cities in the United States.

The exact value of his estate at the time of death is unknown, though today it would likely be worth several billion dollars, due to his substantial holdings in various companies and extensive art collection.

[1] By 1860, Elkins bought out his partner and built the produce operation into the largest store of its kind in the United States.

Elkins and Widener expanded their streetcar enterprise to major cities across the United States including New York, Chicago, Baltimore, St. Louis, Cincinnati and Pittsburgh.

[12] Elkins held sizeable financial positions in American Tobacco Company and International Mercantile Marine Co.[6] Elkins was also involved in real estate and partnered with Widener to purchase large tracts of land in North Philadelphia and build several thousand houses for sale.

In his Elkins Estate at the time of death, he owned and displayed coveted artworks, including works from Donatello, Winslow Homer, Jan Steen, Jean-François Millet, and Jacob Van Ruisdael.

[12] Among his philanthropic gifts, William Elkins left $240,000 to the Masonic Home for Girls in Philadelphia.

A grandson, William McIntire Elkins, was a book collector whose collection of early Americana is held at the Free Library of Philadelphia.