Editing Pittsburgh (section)

===19th century===
{{Further|Pennsylvania in the American Civil War}}
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The federal government recognizes Pittsburgh as the starting point for the [[Lewis and Clark Expedition]].<ref>{{cite news |last1=Bauder |first1=Bob |title=Pittsburgh recognized as starting point for Lewis and Clark expedition |url=https://triblive.com/local/pittsburgh-allegheny/pittsburgh-recognized-as-starting-point-for-lewis-and-clark-expedition/ |agency=Pittsburgh Tribune Review |date=March 10, 2019}}</ref> Preparations began in Pittsburgh in 1803 when [[Meriwether Lewis]] purchased a [[keelboat]] that would later be used to ascend the [[Missouri River]].<ref>{{cite news |last1=O'NEILL |first1=BRIAN |title=Lewis & Clark started here (sorry, St. Louis) |url=https://www.post-gazette.com/opinion/brian-oneill/2018/05/13/brian-o-neill-lewis-and-clark-trail-pittsburgh-mississippi-river/stories/201805130067 |publisher=Pittsburgh Post-Gazette |date=May 13, 2018}}</ref>

The [[War of 1812]] cut off the supply of British goods, stimulating American industry. By 1815, Pittsburgh was producing significant quantities of iron, brass, tin, and glass. On March 18, 1816, the 46-year-old local government became a city. It was served by numerous river steamboats that increased trading traffic on the rivers.

In the 1830s, many [[Welsh people]] from the [[Merthyr]] steelworks immigrated to the city following the aftermath of the [[Merthyr Rising]]. By the 1840s, Pittsburgh was one of the largest cities west of the [[Allegheny Mountains]]. The [[Great Fire of Pittsburgh]] destroyed over a thousand buildings in 1845. The city rebuilt with the aid of Irish immigrants who came to escape the [[Great Famine (Ireland)|Great Famine]]. By 1857, Pittsburgh's 1,000 factories were consuming 22&nbsp;million coal bushels yearly. Coal mining and iron manufacturing attracted waves of European immigrants to the area, with the most coming from [[Germany]].

[[File:Harpers 8 11 1877 Destruction of the Union Depot.jpg|thumb|left|Burning of Union Depot during the [[Pittsburgh railroad strike of 1877]]]]

Because Pennsylvania had been established as a free state after the Revolution, enslaved African Americans sought freedom here through escape as refugees from the South, or occasionally fleeing from travelers they were serving who stayed in the city. There were active stations of the [[Underground Railroad]] in the city, and numerous refugees were documented as getting help from station agents and African-American workers in city hotels. The Drennen Slave Girl walked out of the Monongahela House in 1850, apparently to freedom.<ref name="freedom">William J. Switala, ''Underground Railroad in Pennsylvania'', Stackpole Books, 2001, pp. 88-89</ref> The Merchant's Hotel was also a place where African-American workers would advise slaves the state was free and aid them in getting to nearby stations of the Underground Railroad.<ref name="exhibit">[http://exhibit.library.pitt.edu/freeatlast/fugitive_laws.html Exhibit: ''Free at Last? Slavery in Pittsburgh in the 18th and 19th Centuries''], 2009, University of Pittsburgh Library</ref> Sometimes refugee slaves from the South stayed in Pittsburgh, but other times they continued North, including into Canada. Many slaves left the city and county for Canada after Congress passed the 1850 [[Fugitive Slave Act]], as it required cooperation from law enforcement even in free states and increased penalties. From 1850 to 1860, the black population in Allegheny County dropped from 3,431 to 2,725 as people headed to more safety in Canada.<ref name="freedom"/>

The [[American Civil War]] boosted the city's economy with increased iron and armament demand by the Union. [[Andrew Carnegie]] began steel production in 1875 at the [[Edgar Thomson Steel Works]] in [[North Braddock, Pennsylvania]], which evolved into the [[Carnegie Steel Company]]. He adopted the [[Bessemer process]] to increase production. Manufacturing was key to growth of Pittsburgh and the surrounding region. Railroad lines were built into the city along both rivers, increasing transportation access to important markets.