The rest of his career was spent at D.C. United apart from one season at the New York MetroStars in 2003, and he was the all-time leading scorer in Major League Soccer at the time of his retirement in 2010.

On 22 August 2007, in a match against the New York Red Bulls, he scored his 109th MLS goal, surpassing the previous league record set by former Dallas Burn and Real Salt Lake forward Jason Kreis.

[5] 1998 was Moreno's best season, as he scored 16 goals and added 11 assists, only losing the MLS MVP Award to teammate and fellow Bolivian Marco Etcheverry.

In 2007, he scored his 108th goal on a penalty kick against Toronto FC on 19 May, tying him with Jason Kreis as the all-time leading scorer in MLS.

[6] Moreno was a regular on the Bolivia national team for most of the 1990s and played in the 1994 FIFA World Cup and the 1997 Copa América, but had been ignored for six years until recalled in 2007 for a friendly with Ireland.

He played in the 2007 Copa América, where he scored his eighth international goal in the 39th minute of Bolivia's opening game against the host nation of Venezuela.

[12] The team represents the highest tier in United's Academy, and will begin playing in the Premier Development League, the fourth division in American soccer in 2012.

On 14 September 2013, Moreno was inducted into the D.C. United Hall of Tradition at halftime of a match against the Los Angeles Galaxy at RFK Stadium.