Olin's blasting and gunpowder company expanded into the production of cartridges in 1898 with the formation of the Western Cartridge Company. During World War I, the company created Olin Brass to produce brass for the cartridges. In 1931, Western merged with the famed Winchester Repeating Arms Company. In 1944, the various Olin companies were organized under a new corporate parent, Olin Industries, Inc.
In 1893, Mathieson Alkali Works acquired its neighbor, the Holston Salt and Plaster Corp., and Saltville became a quintessential company town. In Saltville it produced chlorine and caustic soda, producing a considerable amount of methyl mercury—by the company's own estimates, up to 100 pounds per day—into the soils and the North fork of the Holston River. This site was declared a Superfund site in 1982. In 1952, the Mathieson Chemical Company, as it was known by then, acquired the pharmaceutical firm of E.R. Squibb & Sons, spun off in 1968 and now part of Bristol-Myers Squibb.
Olin Industries and Mathieson Chemical Company merged in 1954 to form the Olin Mathieson Chemical Corporation, which adopted the name Olin Corporation in 1969. Under the management of Franklin Olin's sons, John M. and Spencer Truman Olin, it diversified into a wide variety of businesses including forest and paper products, cellophane, bauxite mining, and even camping and skiing gear manufacturing and home construction. It sold off most of these businesses in the 1970s and onwards, finally spinning off its specialty chemicals business on February 8, 1999 as Arch Chemicals, Inc.
Olin announced the sale of its Brass Division in October 2007, but also claimed they lost $140 million in the sale.