Moultrie scored Portland's third goal at the end of the second half.
The 16-year-old got the chance from the start after 39-year-old Christine Sinclair - who won Olympic gold with Canada last summer - was forced to cancel just before the start of the match.
- I am of course very happy to have scored my first goal, but I am even more happy about how important the victory was for the team.
It was a very cool moment overall, says Moultrie according to The Guardian.
Debuted as a 15-year-old
The American midfielder became the youngest to ever play a match in the NWSL a year ago.
As a 15-year-old, she did not reach the NWSL age limit of 18, but after a process of several weeks, Moultrie and the league reached an agreement so that she could play.