Philadelphia Union

Despite being one of the ten largest metropolitan areas in the country and a top-five media market, the Philadelphia area was not represented when Major League Soccer kicked off in 1996. Philadelphia was previously represented by the Philadelphia Atoms (1973–76) and Philadelphia Fury (1978–80) in the FIFA-backed, major professional North American Soccer League (NASL). The Atoms won the Soccer Bowl in their inaugural 1973 season. Philadelphia goalkeeper and Ridley Park, Pennsylvania native Bob Rigby became the first soccer player to be featured on the cover of Sports Illustrated following the club's championship. The Atoms folded after the 1976 season, having been bought by Mexican owners whose plans to move the team to San Antonio were not approved by the league. The Atoms and the Fury both played at Veterans Stadium, though the Atoms played their final season in Philadelphia at Franklin Field. The NASL folded in 1984, leaving the United States without a top-level soccer league until Major League Soccer (MLS) began play in 1996.

The first effort to bring professional soccer back to the Delaware Valley commenced in 2001, when a group of investors attempted to bring an MLS franchise to Trenton, New Jersey. The centerpiece of their efforts was a $31 million soccer-specific stadium to be built across the street from the CURE Insurance Arena and with access to the under-construction NJ Transit River Line. "Union FC" was the intended name for the Trenton MLS team if it came to fruition. However, the MetroStars (now the New York Red Bulls) held the right to block a franchise in Trenton, as it would infringe on their 75-mile competition-free zone.

Five years later, plans were in place to construct a 20,000-capacity stadium on the campus of Rowan University in Glassboro, New Jersey. The stadium would serve as the home field for both an MLS expansion club and Rowan's football team. Ultimately, $100 million in state bonds to fund the stadium and various other improvements on the Rowan campus were dropped by New Jersey Governor Jon Corzine. Shortly after the Rowan proposal fell through, Keystone Sports & Entertainment (the group that would eventually own the Union) looked at a site underneath the Commodore Barry Bridge in Chester to develop a soccer-specific stadium.

In 2007, the Sons of Ben supporter group formed to raise interest toward a Major League Soccer team in Philadelphia. They are credited with demonstrating to MLS an established fan base in the market.

Major League Soccer added Philadelphia as its sixteenth team on February 28, 2008. The finalization of the club was the result of a $47 million package approved by Delaware County politicians and Pennsylvania governor Ed Rendell that included the cost of Subaru Park and a major urban renewal project.

In December 2009, the Union added the Reading Rage youth soccer organization as their official minor league affiliate in the USL Premier Development League. As a result, the Rage were rebranded as "Reading United AC" with a new logo and colors for the 2010 PDL season. In the 2010 MLS SuperDraft, the Union selected forward Danny Mwanga from Oregon State University as the number one pick, as well as sixth and seventh picks Amobi Okugo from UCLA and Jack McInerney from the U.S. U-17 National Team in the first round. In March 2010, the Union signed an affiliation agreement with the Harrisburg City Islanders of the United Soccer League. And in January 2012, the Union formed their first international partnership with Deportivo Saprissa of the Costa Rican Primera División.

The Union played their inaugural game on March 25, 2010, in which they lost 2–0 to Seattle Sounders FC at Qwest Field. Sébastien Le Toux became the first player to score a goal for Philadelphia in their home opener on April 10, 2010, a 3–2 win over D.C. United at Lincoln Financial Field. The team again played Seattle Sounders FC for the first match at Subaru Park on June 27, 2010. Le Toux scored the Union's initial goal at the venue from a penalty kick, which was instrumental to their 3–1 victory. All 12,000 season ticket packages for 2010 were sold prior to this opener. At the end of the inaugural season the Union finished 7th in the Eastern Conference and 14th overall in the league with a record of 8–15–7 (W-L-T).

The Union picked up three players in the 2011 MLS SuperDraft, most notably Zac MacMath, who was the fifth overall draft pick. On January 11, 2011, the Union acquired shirt sponsor Bimbo Bakeries USA. On January 20, Philadelphia introduced two new players: Colombians Faryd Mondragón (GK) and Carlos Valdés (D). Mondragón had recently come from playing with 1. FC Köln in the German Bundesliga, and has at least 50 caps with the Colombia national team. Valdés came from Independiente Santa Fe in the Colombian First Division, where he served as captain before coming to Philadelphia. The Union also signed during the summer transfer window US International Freddy Adu.

The team made a complete turnaround in the 2011 season, finishing 3rd in the Eastern Conference and 8th overall in the league with a record of 11–8–15 (W-L-T) scoring 44 goals and allowing 36. This marked the first time the Philadelphia Union qualified for the MLS Cup Playoffs. The Union had a stellar start of the season that saw them win 4 and only lost 1 of their first six league games. In the 2011 MLS Cup Playoffs the Union lost the first leg of the MLS Eastern Conference semi-finals 2–1 at home on October 30, 2011, with the 1st playoff Union goal coming from Sebastien Le Toux. The Union then lost the 2nd leg 1–0 on November 3, 2011, against the future MLS Cup finalist Houston Dynamo.

John Hackworth became the Union's interim coach on June 13, 2012, receiving the role permanently on August 30, 2012. The Union finished their third season in eighth place in the Eastern Conference and fifteenth in MLS overall, with a record of 10–18–6 (W-L-T), scoring 37 goals and allowing 45. Antoine Hoppenot, who was selected in the third round of the 2012 Supplemental Draft, netted four goals within 817 minutes of play. Subaru Park, then known as PPL Park, was the site of the 2012 MLS All-Star Game in which the MLS All-Stars defeated Chelsea F.C., 3–2. The Union also made it to the semifinals of the 2012 U.S. Open Cup after defeating the Rochester Rhinos 3–0 in the third round and winning against D.C. United on the road 2–1, after extra time, in the fourth round. They subsequently defeated the Harrisburg City Islanders, their main affiliate at the time, 5–2 in the quarterfinals.

The Union traded allocation money in order to take the first overall pick, which was used on goalkeeper and Jamaican international Andre Blake. They then traded down multiple times in order to select Coastal Carolina University midfielder Pedro Ribeiro. Other new, preseason acquisitions included Maurice Edu, French midfielder Vincent Nogueira, Argentinian midfielder Cristian Maidana, and former MLS Rookie of the Year defender Austin Berry. Despite these additions, the Union still languished in mediocrity, winning just two of their first 14 games, posting a record of 2–7–5 (W-L-T). On April 20, 2014, the Union traded forward Jack McInerney to the Montreal Impact for winger Andrew Wenger, a Lancaster, Pennsylvania native. Hackworth's coaching career with the Union ended on June 10, 2014.

Although failing to make the playoffs, the Union reached the 2014 Lamar Hunt U.S. Open Cup finals for the first time in the club's history. During the offseason, the club traded for forward C. J. Sapong from Sporting Kansas City. They also traded long time defensive midfielder Amobi Okugo to Orlando City SC. Other new preseason acquisitions included FC Nantes loanee Fernando Aristeguieta, S.L. Benfica loanee Steven Vitória, and free agent Cameroonian 18-year-old midfielder Eric Ayuk. During the 2015 MLS SuperDraft the Union drafted forward Dzenan Catic from Bosnia-Herzegovina, midfielder Eric Bird, and defender Raymond Lee. During the expansion draft, Orlando City SC drafted Philadelphia midfielder Pedro Ribeiro. Despite all the offseason transactions, the Union only registered one win in their first ten league games with a record of 1–6–3 (W-L-T).

During the 2015 summer transfer window, the Union traded longtime defender Sheanon Williams to the Houston Dynamo for allocation money, which they used to sign Swiss midfielder Tranquillo Barnetta on July 29, 2015. The club achieved a successful run in the 2015 Lamar Hunt U.S. Open Cup, earning a second consecutive appearance in the Open Cup final. This match took place against Sporting Kansas City, at Subaru Park on September 30, 2015.

In 2016, the Union would acquire Chris Pontius from D.C. United, Surinames midfielder Roland Alberg, and Brazilian right midfielder Ilsinho. They would also acquire U.S. international Alejandro Bedoya in the summer transfer window. The Union would also add key players from the 2016 MLS SuperDraft including Josh Yaro, Keegan Rosenberry, and Fabian Herbers. The 2016 season saw success from Goalkeeper Andre Blake who later would win the 2016 MLS Goalkeeper of the Year Award. The Union were in constant playoff contention, however went 0–5–2(W-L-T) in the final 7 matches of the regular season. The Union would still reach the playoffs for only the 2nd time in team history, beating out New England Revolution on goal differential. The Union were beaten 3–1 in the Knockout round of the 2016 MLS Cup Playoffs by Toronto FC.

The Union were unable to build on their 2016 success, finishing with the same record but still missing the playoffs in 2017. Despite failing to make the playoffs, Curtin was announced to retain his head coach position for the 2018 season.

A snake mascot, Phang, was introduced on September 10, 2018. Ahead of the 2019 season, Union Sporting Director, Ernst Tanner, announced that Curtin would be retained for the upcoming season on a one-year extension. By July of that season, the Union reach first place in the Eastern Conference and hitting the club's best start to a season. This success lead to the club announcing Curtin signed a two-year contract extension, to remain head coach through the 2021 season.

The 2020 season was the most successful to date for the Union. Despite disruptions from the COVID-19 pandemic, the Union reached the semi-final of the MLS is Back Tournament and went on to win their first trophy finishing top of the league standings and earning the 2020 Supporters' Shield. The team's performance over the season earned Curtin his first Sigi Schmid Coach of the Year Award. Winning the Supporter's Shield earned the Union their debut in the CONCACAF Champions League, where the Union earned their first international win against Deportivo Saprissa; a victory that marked Curtin's 100th win as head coach of the club.

Within two days prior to the Union's first ever conference final match in team history, it was reported that 11 players, including six starters had to undergo the league's COVID-19 protocol. Philadelphia lost to eventual champions New York City FC 2–1. It was later stated that it would've been impossible to delay the game, as the players would not have been available for the MLS Cup Final.

On July 8, 2022, the Philadelphia Union defeated D.C. United 7–0, setting a club record and tying the MLS record for biggest goal differential win. The overall season proved to be special, as Philadelphia topped the Eastern table with 67 points—equal with Supporters' Shield winners Los Angeles FC (and with better goal differential but lost out due to MLS' tiebreaker of total wins). Philadelphia beat FC Cincinnati in the conference semifinals, 1–0, on a Leon Flach goal, and then defeated defending champions New York City FC 3–1 in the conference finals to advance to their first-ever MLS Cup final.

In MLS Cup, the Union erased 1−0 and 2−1 deficits and center back Jack Elliott scored twice in the match, including late in extra time. Ultimately LAFC came back to force penalties and won the Cup in a penalty shoot-out.