Editing Pennsylvania (section)

===20th century===
[[File:Bethlehem_Steel.jpg|thumb|[[Bethlehem Steel]] in [[Bethlehem, Pennsylvania|Bethlehem]] was one of the world's leading steel manufacturers for most of the 19th and 20th century. In 1982, however, it discontinued most of its operations, declared bankruptcy in 2001, and was dissolved in 2003.]]

In the beginning of the 20th century, Pennsylvania's economy was centered on steel manufacturing, [[logging]], [[coal mining]], [[textile]] production, and other forms of industrial [[manufacturing]]. A surge in immigration to the U.S. during the late 19th and early 20th centuries provided a steady flow of cheap labor for these industries, which often employed children and people who could not speak English from [[Southern Europe|Southern]] and [[Eastern Europe]].{{Citation needed|date=March 2022}} Thousands of Pennsylvanians volunteered during the [[Spanish–American War]]. Pennsylvania was an important industrial center during [[World War I]]. The state provided over 300,000 soldiers during the war. On May 31, 1918, the [[Pittsburgh Agreement]] was signed in [[Pittsburgh]], signed by [[Tomáš Masaryk]] and established [[Czechoslovakia]] as an independent nation. 

In 1922, 310,000 Pennsylvania miners joined the [[UMW General coal strike (1922)|UMW General coal strike]], which lasted 163 days and shut down most of the state's coal mines.<ref>{{Cite web |last=Humanities |first=National Endowment for the |date=August 5, 1922 |title=The labor world. [volume] (Duluth, Minn.) 1896–current, August 05, 1922, Image 1 |url=https://chroniclingamerica.loc.gov/lccn/sn78000395/1922-08-05/ed-1/seq-1/ |via=chroniclingamerica.loc.gov}}</ref><ref>{{Cite news |last=Zimand |first= |orig-date=May 1922. Print |title=Labor Age |pages=4–7, 15–17 |url=https://archive.org/details/v11n05-may-1922-LA/page/n5/mode/2up |access-date=March 2, 2023}}</ref>

In 1923, [[Calvin Coolidge|President Calvin Coolidge]] established the [[Allegheny National Forest]] under the authority of the [[Weeks Act]] of 1911.<ref>{{Cite web |title=About the Area |url=https://www.fs.usda.gov/main/allegheny/about-forest/about-area |url-status=dead |archive-url=https://web.archive.org/web/20120314033332/http://www.fs.usda.gov/main/allegheny/about-forest/about-area |archive-date=March 14, 2012 |access-date=July 30, 2018}}</ref> The forest is located in the northwest part of the state in [[Elk County, Pennsylvania|Elk]], [[Forest County, Pennsylvania|Forest]], [[McKean, Pennsylvania|McKean]], and [[Warren County, Pennsylvania|Warren]] Counties for the purposes of timber production and watershed protection in the [[Allegheny River]] basin. The Allegheny is the state's only national forest.<ref>{{cite web |title=The National Forests of the United States |url=https://foresthistory.org/wp-content/uploads/2017/01/National-Forests-of-the-U.S.pdf |url-status=live |archive-url=https://web.archive.org/web/20121028014355/http://www.foresthistory.org/ASPNET/Places/National%20Forests%20of%20the%20U.S.pdf |archive-date=October 28, 2012 |access-date=June 16, 2018 |publisher=Forest History Society}}</ref>

During [[World War II]], Pennsylvania manufactured 6.6 percent of total U.S. military armaments for the war, the sixth-most of the 48 states.<ref>[[Whiz Kids (Department of Defense)|Peck, Merton J.]] & [[Frederic M. Scherer|Scherer, Frederic M.]] ''The Weapons Acquisition Process: An Economic Analysis'' (1962) [[Harvard Business School]] p. 111</ref> [[Philadelphia Naval Shipyard]] served as an important naval base during the war, and Pennsylvania produced many of the war's most important military leaders, including [[George C. Marshall]], [[Henry H. Arnold|Hap Arnold]], [[Jacob L. Devers|Jacob Devers]], and [[Carl Spaatz]]. During World War II, over a million Pennsylvanians served in the armed forces, and more [[Medal of Honor|Medals of Honor]] were awarded to Pennsylvanians than to individuals from any other state.{{Citation needed|date=March 2022}}

On March 28, 1979, the [[Three Mile Island accident]] was the most significant [[Nuclear and radiation accidents and incidents|nuclear accident]] in U.S. commercial nuclear power plant history.<ref>{{cite web |date=June 21, 2018 |title=Backgrounder on the Three Mile Island Accident |url=https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/3mile-isle.html |url-status=live |archive-url=https://web.archive.org/web/20190824203624/https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/3mile-isle.html |archive-date=August 24, 2019 |access-date=August 24, 2019 |website=[[Nuclear Regulatory Commission]]}}</ref><ref>{{cite news |last1=King |first1=Laura |last2=Hall |first2=Kenji |last3=Magnier |first3=Mark |date=March 18, 2011 |title=In Japan, workers struggling to hook up power to Fukushima reactor |newspaper=Los Angeles Times |url=https://www.latimes.com/world/la-xpm-2011-mar-18-la-fgw-japan-quake-main-20110319-story.html |url-status=live |access-date=August 24, 2019 |archive-url=https://web.archive.org/web/20110322152850/http://articles.latimes.com/2011/mar/18/world/la-fgw-japan-quake-main-20110319 |archive-date=March 22, 2011}}</ref> The state was hard-hit by the decline and restructuring of the steel industry and other heavy industries during the late 20th century. With job losses came heavy population losses, especially in the state's largest cities. Pittsburgh lost its place among the [[List of most populous cities in the United States by decade|top ten most populous cities in the United States]] in 1950, and Philadelphia dropped to the fifth and is currently the [[List of United States cities by population|sixth-largest city]] after decades of ranking among the top three.

After 1990, as information-based industries became more important in the economy, state and local governments put more resources into the old, well-established public library system. Some localities, however, used new state funding to cut local taxes.<ref>William F. Stine, "Does State Aid Stimulate Public Library Expenditures? Evidence from Pennsylvania's Enhancement Aid Program" ''Library Quarterly'' (2006) 76#1 107–139.</ref> New ethnic groups, especially [[Hispanic and Latino Americans|Hispanics and Latinos]], began entering the state to fill low-skill jobs in agriculture and service industries. For example, in [[Chester County, Pennsylvania|Chester County]], [[Mexican Americans|Mexican]] immigrants brought the [[Spanish language]], increased [[Catholicism]], high birth rates, and cuisine when they were hired as agricultural laborers; in some rural localities, they made up half or more of the population.<ref>Victor M. Garcia, "The Mushroom Industry And The Emergence Of Mexican Enclaves In Southern Chester County, Pennsylvania, 1960–1990" ''Journal of Latino-Latin American Studies (JOLLAS)'' (2005) 1#4 pp 67–88.</ref>

[[Stateside Puerto Ricans]] have built a large community in the state's third-largest city, [[Allentown, Pennsylvania|Allentown]], where they comprise over 40% of the city's population as of 2000.<ref>Gilbert Marzan, "Still Looking for that Elsewhere: Puerto Rican Poverty and Migration in the Northeast." ''Centro Journal'' (2009) 21#1 pp 100–117 [https://www.redalyc.org/pdf/377/37721248005.pdf online].</ref>

In the late 20th century, as Pennsylvania's historical national and even global leadership in [[mining]] largely ceased and its [[steelmaking]] and other heavy manufacturing sectors slowed, the state sought to grow its service and other industries to replace the jobs and economic productivity lost from the downturn of these industries. Pittsburgh's concentration of universities has enabled it to be a leader in technology and healthcare. Similarly, Philadelphia has a concentration of university expertise. Healthcare, retail, transportation, and tourism are some of the state's growing industries of the postindustrial era. As in the rest of the nation, most residential population growth has occurred in suburban rather than central city areas, although both major cities have had significant revitalization in their downtown areas.<ref>Ashok K. Dutt, and Baleshwar Thakur, ''City, Society, and Planning'' (Concept Publishing Company, 2007) pp. 55–56</ref> Philadelphia anchors the [[List of Metropolitan Statistical Areas|seventh-largest]] [[metropolitan area]] in the country and one of the largest metropolitan areas in the world, and Pittsburgh is the center of the nation's 27th-largest metropolitan areas. As of 2020, the [[Lehigh Valley]] in eastern Pennsylvania is the nation's 69th-largest metropolitan area.<ref name="Kraus2">{{cite news |last1=Kraus |first1=Scott |title=No end in sight to Valley's population growth |url=https://www.mcall.com/2012/07/14/no-end-in-sight-to-valleys-population-growth/ |url-status=live |access-date=December 1, 2014 |archive-url=https://web.archive.org/web/20121007013920/http://articles.mcall.com/2012-07-14/news/mc-allentown-growth-figures-20120714_1_population-growth-new-residents-macungie-and-bethlehem-townships |archive-date=October 7, 2012}}</ref> Pennsylvania also has [[List of Metropolitan Statistical Areas|six additional metropolitan areas]] that rank among the nation's 200-most populous metropolitan areas. Philadelphia forms part of the [[Northeast megalopolis]] and is associated with the [[Northeastern United States]]. Pittsburgh is part of the [[Great Lakes megalopolis]] and is often associated with the [[Rust Belt]].