U.S. Steel Corp., the 113-year-old metal producer, will be replaced in the Standard & Poor’s 500 Index by Martin Marietta Materials Inc. The company founded by J.P. Morgan and steel magnates including Andrew Carnegie is too small for the American equity benchmark, according to a statement from S&P Dow Jones Indices. The company, with a market value of $3.8 billion, will be added to the S&P MidCap 400 Index at the close of trading on July 1. http://www.bloomberg.com/news/2014-06-27/u-s-steel-will-be-replaced-in-s-p-500-by-martin-marietta.html