It's part of the Highline Schools Foundation's fifth annual "Project Promise" event. There are 18,000 students in the Highline School District and 13,000 of them live below the poversty line.
More than 100 girls from lower income families got to pick the dress of their dreams from a collection of donated gowns.
"Hopefully by the time they leave they have not only a dress but it'll fit because we have alterations and some jewelery and shoes before they go home," said Ashley Fosberg, executive director of the Highline Schools Foundation.
Organizers say no one should miss prom just because they can't afford it.
"Why not? why not help them have that final moment when they can celebrate and graduate in style, just like everybody else," Fosberg said.
The girls are allowed to keep the dresses or they can return them to be used the following year.