John Barnard Swett Pearse was born on April 19, 1842, in Philadelphia, Pennsylvania.

He was an American engineer, metallurgist, chemist, and author. His father, Oliver Peabody Pearse (1808-1848), a merchant sea-captain, was drowned at Cape May, New Jersey while saving a bather when John was six years of age. His mother, Adelia Coffin Swett (1817-1891), later married Dr. Edward Hartshorne (1818-1885), a metallurgical expert whose experiences and influence determined the boy's active business career. He graduated from Yale (B.A., 1861) and continued to study metallurgy in the School of Mines at Freiberg, Saxony. In 1863, he took charge of the chemical division of the U.S. Army's laboratory at Philadelphia. In 1870, he became general manager of the Pennsylvania Steel Works, where he built up an enviable reputation as a metal expert, particularly in designing and improving Bessemer steel plants and their products. In 1874, he started appointment as Commissioner and Secretary of the 2nd Pennsylvania Geological Survey, a position he held until 1881. In 1876, Pearse became General Manager of the South Boston Iron Company. Due to his health problems, he retired in 1883. He was the author of several publications, the largest being his historical essay, "A Concise History of the Iron Manufacture of the American Colonies up to the Revolution and of Pennsylvania until the Present Time" (1876).

In 1876, he married Mary Langdon Williams (1842–1915). He died on August 24, 1914, at his summer residence in Georgeville, Quebec.