busiest freight corridors, the Pittsburgh Line, and operates up to 70 trains per day through the city. The suburban Conway Rail Yard—originally built in 1889—was the largest freight rail center in the world from 1956 until 1980 and is today the nation's second-largest. CSX, the other major freight railroad in the eastern U.S. also has major operations around Pittsburgh. Port The Port of Pittsburgh ranks as the 20th-largest port in the United States with almost 34 million short tons of river cargo for 2011, the port ranked 9th-largest in the U.S. when measured in domestic trade. Notable people Sister cities Pittsburgh's sister cities are: Bilbao, Spain Da Nang, Vietnam Fernando de la Mora, Paraguay Gaziantep, Turkey Glasgow, Scotland Karmiel, Israel Matanzas, Cuba Misgav, Israel Naucalpan, Mexico Ostrava, Czech Republic Prešov, Slovakia Saarbrücken, Germany Saitama, Japan San Isidro, Nicaragua Sheffield, England Skopje, North Macedonia Sofia, Bulgaria Wuhan, China Zagreb, Croatia See also Greater Pittsburgh Region List of fiction set in Pittsburgh List of municipalities in Pennsylvania List of people from Pittsburgh Explanatory notes References Further reading Allen Dieterich-Ward, Beyond Rust: Metropolitan Pittsburgh and the Fate of Industrial America (U of Pennsylvania Press, 2016). viii, 347 pp. Kenneth J. Kobus, City of Steel: How Pittsburgh Became the World's Steelmaking Capital During the Carnegie Era. Lanham, MD: Rowman and Littlefield, 2015. Charles McCollester, The Point of Pittsburgh: Production and Struggle at the Forks of the Ohio. Pittsburgh, PA: Battle of Homestead Foundation, 2008. External links Pittsburgh Convention and Visitors Bureau – Tourism Historic Pittsburgh Maps Collection PittsburghTODAY Regional benchmarks and statistics Pittsburgh Daily Gazette, Google Newspaper archive. PDFs of 5,794 issues, dating primarily 1834–1841 and 1850–1863. Cities in Allegheny County, Pennsylvania Cities in Pennsylvania County seats in Pennsylvania Inland port cities and towns of Pennsylvania Pennsylvania populated places on the Monongahela River Pennsylvania populated places on the Ohio River Pittsburgh metropolitan area Populated places established in 1758 World War II Heritage Cities