The company began as the Repauno Chemical Company on June 7, 1880, founded by Lammot du Pont (1831-1884). Lammot du Pont was a chemist working for the family business E.I. du Pont de Nemours & Company, a chemical company that originally produced gunpowder. Additional subscriptions were secured from E.I. du Pont de Nemours & Company (DuPont Company), the Laflin & Rand Powder Company, and the Hazard Powder Company, the latter already controlled by the DuPont Company. Initially, the DuPont Company did not get involved in dynamite production directly; it felt the product was too new and dangerous, but it supported Lammot du Pont in its efforts. The company built its works at a remote site on the Delaware River near Gibbstown, New Jersey, taking its name from nearby Repauno Creek Explosions claimed a number of lives over the course of dynamite production, including Lammot du Pont’s in an explosion in 1884.

The Eastern Dynamite Company was incorporated in New Jersey on June 28, 1895, for the purpose of acquiring the stocks of the Repauno Chemical Company, the Hercules Powder Company in California, and the Atlantic Dynamite Company and operating them in the interest of the big three gunpowder producers. In 1902, the cousins Alfred I. du Pont (1864-1935), Pierre S. du Pont (1870-1954), and T. Coleman du Pont (1863-1930) acquired control of DuPont, Laflin & Rand, and Hazard, and in the following year they vested all operations in the E.I. du Pont de Nemours Powder Company. The Repauno Chemical Company was merged into the Eastern Dynamite Company in May 1904. In 1902, the du Ponts built the Eastern Laboratory, one of their first research facilities, at the Repauno Works.

In 1912, DuPont was ruled in violation of the antitrust laws, and to restore competition, parts of its assets were transferred to two new, independent firms, the Atlas Powder Company, and the Hercules Powder Company. Under this plan, the Eastern Dynamite Company was dissolved, and its plants were distributed among the new companies. The Repauno Works stayed with E.I. du Pont de Nemours & Company as part of its Explosives Department.