Eagles–Steelers rivalry

Both teams were officially founded in 1933, with the Steelers then being known as the Pittsburgh Pirates. However, their histories predate that, with the Steelers being known as the J.P. Rooneys dating to 1921 as a semipro team, while the Eagles are arguably descended from the Frankford Yellow Jackets based in Philadelphia's Frankford neighborhood dating to 1899. The NFL considers both teams having started in 1933 alongside the now-defunct Cincinnati Reds. Both teams took advantage of Pennsylvania relaxing their blue laws in 1933 that previously didn't allow sporting events on Sundays, when most NFL games took place. The blue laws, combined with general issues related to The Great Depression, were among the reasons the Yellow Jackets failed despite winning the NFL champsionship in 1926.

The first meeting between the teams was on November 19, with the Eagles winning, 25–6. The two teams would struggle their first decade in the NFL both on the field and financially, with the Steelers staying afloat mostly due to team founder Art Rooney's gambling habits. Eventually, in late 1940 Rooney sold the Steelers to Alexis Thompson, a 26-year-old steel heir from Boston frequently described in the press as "a well-heeled New York City playboy". Thompson planned to move the franchise to Boston and play games in Fenway Park. Eagles owner Bert Bell brokered the deal between Rooney and Thompson for $160,000, and Rooney used $80,000 of the proceeds to buy a partnership in the Eagles, which at the time was owned by Bell. The deal also involved the trade of several players between the two teams.

The two owners planned to field a combined Philadelphia-Pittsburgh team called the Pennsylvania Keystoners that would play home games in both cities. The original proposition was that Thompson would buy the franchise and take the Pittsburgh club to Boston and Bell and Rooney would pool their interests in the Eagles to form a Philadelphia-Pittsburgh club, splitting the home games between Forbes Field in Pittsburgh and Philadelphia's Municipal Stadium. Thompson, however, was unable to secure a place to play in Boston. After meeting with Rooney, plans changed whereby Thompson's club (ostensibly the former Steelers) would play in Philadelphia as the Eagles, while the Rooney-Bell owned team would play in Pittsburgh as the Steelers, effectively trading the two clubs between their cities.

The notion for a single team between the two cities was revived, when for one season in 1943, forced to do so by player shortfalls brought on by World War II, the two clubs temporarily merged as the Philadelphia-Pittsburgh "Steagles". The league only approved the merger for one year; Pittsburgh was willing to merge again for 1944 but not Philadelphia. This forced the Steelers to merge with the Chicago Cardinals (as Card-Pitt) for 1944.

Following the end of the war, both teams fortunes changed, with the Eagles and Steelers both clinching playoff spots in the late 1940s, including their only postseason meeting to date in 1947, when the Eagles shut out the Steelers 21–0 at Forbes Field. It would be the Steelers only playoff appearance until the Immaculate Reception 25 years later. The Eagles, under head coach Greasy Neale, won NFL championships in 1948 and 1949.

During the 1950s and 1960s, both teams success and failures would be relative to one another, to the point that both teams would be "competing" for the worst record in the NFL in 1968 and the chance to draft O.J. Simpson. Ultimately, the Atlanta Falcons had the NFL's worst record and the Buffalo Bills of the American Football League would win out on what was at that point the common draft. The Eagles, drafting third, would select Leroy Keyes while the Steelers, drafting fourth, would draft relative unknown Joe Greene. New Steelers head coach Chuck Noll would say later that the team would've drafted Greene even if it had the first overall pick, while Keyes (like Simpson a running back) was viewed by Eagles fans as more of a "consolation prize". Ultimately (Simpson's successful NFL career aside), Keyes lasted five years in the NFL; Greene would become a key member of the Steel Curtain defense and is now a member of the Pro Football Hall of Fame and one of two Steelers to have their number officially retired.