Peter Nowak's first season with United gave him the distinction of being the first person to win the MLS Cup as a player and head coach. As a player for the Chicago Fire, Nowak was named MLS Cup '98 MVP for his two assists during the Fire's 2-0 victory over United. He also started in the 2000 MLS Cup against the Kansas City Wizards, which resulted in 0-1 loss. His teammate at the time, Josh Wolff, who played as a substitute in that match, would score Kansas City Wizards's first goal in the 2004 MLS Cup.
While United barely surpassed a .500 record, the Wizards entered the playoffs as the most victorious team of the regular season.
United won 10 of their final 12 regular season games. Winning the MLS Cup completed a seven-game winning streak. Their last loss was on September 25, 2004 against the Columbus Crew.
D.C. United players and coches celebrating their win in the 2004 Eastern Conference Championship.
After dominating the league in the first four years of Major League Soccer's existence, D.C. United's entered a rough patch in the early 2000s, failing to make the playoffs in the next three seasons following their 1999 championship. The previous season, D.C. United made a return into the playoffs, but were immediately eliminated by Chicago Fire, losing both matches by 2–0 margins.
Entering the 2004 season, club management hired for Chicago Fire standout, Piotr Nowak as the club's head coach, making Nowak the first ex-MLS player to subsequently manage a team. Throughout a majority season, the club was inconsistent on the field, failing to post back-to-back wins through the first 24 weeks of the campaign. However, following the team's 3–0 home victory to Dallas Burn, the club won four of their remaining five matches, and climbed into second place in the Eastern Conference, and fourth place overall.
The second-seeded United played host to their Atlantic Cup rivals, MetroStars in the Eastern Conference Semifinals. Both matches of the two-legged aggregate series, ended in 2–0 victories for United, as they advanced to the Eastern Conference championship winning the semifinal series, 4–0.
Considered ones of the greatest matches in Major League Soccer history, the match ended drawn at 3–3 after New England's Pat Noonan tied the game in the 85th minute. With no clear victor in extra time, the Eastern Conference championship was decided through the virtue of penalty kicks. In the first round of penalties, both United's Ben Olsen and the Revolution's Steve Ralston missed their penalties. The next two penalty takes from both sides scored in the shootout. The third round of penalties saw United's Alecko Eskandarian score, but New England's Jay Heaps miss. In the fourth round, the fortunes switched, as New England's Shalrie Joseph scored, but United's Jaime Moreno missing, causing the shootout to go to sudden death. In the first round, New England's Clint Dempsey had his shot hit the post, while United's Brian Carroll scored the match-winning penalty kick, sending D.C. United into their fifth-ever MLS Cup final.
The Kansas City Wizards were returning to the MLS Cup final for the second time in club history, the last being in 2000, in which they emerged victorious over Chicago Fire. It was the same year that the Wizards earned their first, so far only, "league double" earning the Supporters' Shield along with the MLS Cup title. During the regular season, the Wizards had the highest total number of regular season wins. Despite that, the Wizards fell short of the league premiership, due to tiebreakers, but emerged as Western Conference regular and postseason champions, while earning their first ever U.S. Open Cup title.
Kansas City began their postseason campaign by playing the San Jose Earthquakes, the defending MLS Cup champions, in the Western Conference Semifinals. The first leg of the aggregate series was played in San Jose, and the match ended in the Earthquakes' favor, as the club posted a 2–0 victory over the Wizards. Since the away goals rule is not used in the MLS Cup Playoffs, the Wizards needed an at least a two-goal victory to send the series to extra time, or a three-goal win to advance to the Western Conference Final. An own goal from San Jose, along with goals from Khari Stephenson and Jack Jewsbury during regulation time gave Kansas City a 3–2 aggregate victory, and sent the Wizards to the Conference Final for the second straight year.
The 2004 Western Conference Final saw the top-seeded Kansas City take on second-seed, Los Angeles Galaxy. The series was a rematch of the 2002 Western Conference Semifinals, in which the Galaxy defeated the Wizards 2–1 in a best-of-three series. However, during the 2004 regular season, Kansas City had not lost to Los Angeles during any of the four outings, winning and drawing twice, each. The Western Conference championship saw Kansas City's Davy Arnaud netting twice to send the Wizards to their second straight league championship.
For the second consecutive season, Carson's The Home Depot Center was selected to host the MLS Cup championship, the first time a stadium has hosted consecutive MLS Cup championships (the Home Depot Center would again host back to back MLS Cups in 2011 and 2012).
Due to limited seating capacity it was the first MLS Cup sellout.
United responded with three goals in only seven minutes.
Dema Kovalenko received the first red card in MLS Cup history when he blocked a Kansas City shot with his arm while standing on the goal line. Josh Wolff scored his first career playoff goal on the resulting penalty kick. It was the first penalty kick scored in MLS history.
Adu's substitution in the 65th minute made him the youngest member of an American professional championship team in modern sports history.
After the game Eskandarian stated, "I didn't even know where the ball hit me. It was just what you learn in youth soccer; you keep going until you hear a whistle." On August 19, 2011 Eskandarian publicly stated that there was a handball on the play that led to his second goal.
The Wizard's head coach, Bob Gansler, complimented United's defensive performance:
To use an old bit of soccer wisdom, you play about as well as your opponent lets you.