Played at SeatGeek Stadium immediately after Chicago Fire's MLS clash against Colorado Rapids, an action packed first half saw the game tied at 2-2 at the half-time interval.
Portland took the lead early through Canadian legend Christine Sinclair, before Yuki Nagasato equalised for Chicago from the penalty spot. Chicago's Kerr then harassed the visiting defenders into giving up possession to make it 2-1, with Portland's Ana-Maria Crnogorčević levelling.
As in the first half, Sinclair also opened the scoring in the second half, but Chicago substitute Michele Vasconcelos made it 3-3 with just under 15 minutes left to play. The go-ahead goal came from Portland in the 87th minute as Sinclair competed a hat-trick from the penalty spot, but Nagasato ensured the points were shared with an even later strike to make it 4-4.
That makes it two draws to kick off 2019 for Chicago, while Portland have four points so far.
An early bicycle kick from Orlando Pride defender Alanna Kennedy was the standout goal in her team's 1-1 draw with Reign FC in Tacoma, Washington. The game also saw a first professional goal from Reign's Bethany Balcer to level the scores in the first half.
Bizarrely, this is the sixth straight draw between Reign and Pride, with five of those ending 1-1.
Elsewhere, there was a second defeat of the season for Carli Lloyd and Sky Blue after Houston Dash visited New Jersey and took all three points. A solitary late goal from Dash midfielder Sofia Huerta was the difference, while Lloyd had actually missed a penalty in the first half.
If anything the margin of victory for the visitors could have been much greater, as Sky Blue goalkeeper Kailen Sheridan made as many as 10 saves.
Having been out of action in week one of the season, Utah Royals opened with a win by beating Washington Spirit at Rio Tinto Stadium in Sandy, Utah. Lo'eau LaBonta scored the only goal of the match to give them a 1-0 win after being assisted by USWNT forward Christen Press.
There was also a momentous moment in this one for Royals midfielder Mandy Laddish, who came off the bench in the closing stages for her first action since 2016 after missing each of the last two NWSL seasons following two hip surgeries.
At the end of week two, North Carolina Courage are top of the standings, but remain level on points with Portland Thorns and Houston Dash, who are second and third respectively. Sky Blues are the only team in the league yet to claim a point after two straight defeats.