Pro women’s soccer is having a moment. Here’s how to make it last

The commissioner of National Women’s Soccer League tells Fortune about his plan to turn the excitement over the Women’s World Cup win into a booming pro league.

On Wednesday, July 22, the National Women’s Soccer League’s (NWSL) Portland Thorns played the Seattle Reign in front of a league record-setting crowd of 21,144 at Portland’s Providence Park.

(The previous record, 19,123, was set in Portland last August.) What’s more, the NWSL reports that roughly half of the games played since the 2015 Women’s World Cup have been sell-outs, with advance tickets are selling faster than in previous years.

Women’s win at the recent World Cup, which turned a number of league players Carli Lloyd, Megan Rapinoe and Tobin Heath, to name a few into household names.

He’s excited about the Portland attendance numbers and says he’s seeing growth happen across the league, but cautions that building to regular sell-out matches will take time.

When reports surfaced that the women’s national team would take home $2 million for its win, compared to the $35 million paid to Germany’s World Cup-winning team in 2014, concerns about a pay gap in women’s soccer emerged.

NWSL teams have a salary cap of $200,000, According to Atlas, a data web site, the minimum salary in the NWSL is $6,842, while the men’s soccer league floor is $60,000.

Currently, the league’s nine clubs are the Boston Breakers, Chicago Red Stars, Houston Dash, FC Kansas City, Portland Thorns FC, Seattle Reign FC, Sky Blue FC, the Washington Spirit and the Western New York Flash.

He also sees opportunity for international expansion, especially through the league’s support from the Canadian Soccer Association and Federation of Mexican Football, as well as the United States Soccer Federation.