Atlanta United blown away 6-1 by the Columbus Crew, Morris' four-goal haul lifts Seattle
Atlanta boasted three wins and a draw from their first four matches of the season – and had won their past two by a combined margin of 8-1 – but they were no match for an inspired Columbus outfit in front of their home fans.
Crew forward Christian Ramirez bagged a brace in the second half, while Alexandru Matan was credited with three assists in Columbus' second win of the campaign.
Meanwhile, Seattle Sounders striker Jordan Morris raced out into the Golden Boot lead with a four-goal haul in his side's 4-1 away win against Sporting Kansas City.
The 28-year-old American more than doubled his three goals from the opening four matches, opening up a two-goal lead on rest of the competition.
With Atlanta going down, it was the New England Revolution capitalising and taking over as the Eastern Conference leaders, overcoming a first-half strike from Christian Benteke to defeat D.C. United 2-1.
The loss left D.C. near the bottom of the standings with four points from five matches, where they are joined by Charlotte after their 1-1 home draw against New York Red Bulls.
Cincinnati are the only undefeated team in the East through five matches, securing their third win with a 1-0 triumph over Nashville, to go with two draws as they sit one point behind New England.
A 92nd-minute winner gave the Chicago Fire a 3-2 victory away from home against Inter Miami – their first win of the season – while two goals in the first 10 minutes were enough for Orlando City to prevail 2-1 against the Philadelphia Union.
LA Galaxy remain winless after battling out a 0-0 draw against the Portland Timbers, while it was more dramatic for the Vancouver Whitecaps as they needed a 98th minute equaliser to snatch a point in their 1-1 tie with Minnesota.
Austin FC let a golden opportunity to climb the Western Conference slip away as they dropped points in a 1-1 home draw against the cellar-dwelling Colorado Rapids, who doubled their points tally for the season with the result.
A 55th-minute penalty from Amine Bassi was enough to give the Houston Dynamo a 1-0 win against New York City, while expansion side St. Louis City continued their perfect start to their first season with a convincing 4-0 drubbing of Real Salt Lake, leaving them the only side with the maximum 15 points from five matches.
In the late window, Los Angeles FC benefitted from a first-half red card to defeat FC Dallas 2-1, while Toronto FC battled out a scoreless draw with the San Jose Earthquakes.