Clark Oil settles in region in 1945An aerial view of Clark Oil Refining Corporation’s Chicago Refinery was acquired in 1945, consisted of a crude topping unit and a thermal cracking unit — capacity 5,000 barrels per day. In the intervening years, new facilities were built at the Blue Island site, which included a Houdry catalytic cracking unit in 1951 andPhoto courtesy of Clark Oila UOP Platformer was added in 1954. In midyear of 1958, a UOP Fluid Cat Cracker and UOP Alkylation unit went on stream. These improvements upgraded product quality and raised the gasoline yields to an enviable level in the refinery operations, according to a corporate brochure published in 1963.