Across the Monongahela River from the old Homestead Steel Plant site are the remains of the Carrie Furnaces, one of the largest preserved remains of the steel industry in the USA. There used to be seven blast furnaces here, smelting iron for the mills at Homestead, which was transported by rail to the plant over a hot metal bridge. The first furnaces were built in 1884, and they went offline in 1978. Only two furnaces remain, numbers 6 and 7, with surrounding buildings. They are being preserved by the Rivers of Steel Heritage Corporation and are sometimes open for public tours. Though other blast furnaces are visible from public space, these, and the Sloss furnaces in Alabama, are the only ones in the country where the public is allowed to wander inside.