North Carolina Courage players celebrate their NWSL soccer title victory over the Thorns in Portland, Ore., on Sept. 22. (AP file photo)

Megan Rapinoe, the lavender-haired icon of women’s soccer, maintains that green is the key to her sport’s sustainability.

“For me, it’s about the Benjis,” she said.

Women’s soccer engages the U.S. every four years, then disappears for most fans like a comet leaving the solar system. In the wake of the Americans’ record-setting fourth World Cup title Sunday, the hard part remains: the weekly work of boosting the National Women’s Soccer League, where average attendance remains at a minor league level.

Fans have not handed over a sufficient supply of $100 bills displaying Benjamin Franklin’s portrait, and sponsors and broadcasters have not made enough of the six-, seven- and eight-figure agreements needed for the NWSL to rise to the level of men’s Major League Soccer.

“On the men’s side in MLS, they have owners with extremely deep pockets,” defender Crystal Dunn said. “If the women’s game is going to grow, it’s going to come down to us not kind of penny-pinching on things and really putting a lot of resources in.”

The Women’s United Soccer Association, launched as the first fully professional women’s league, folded in 2003 after just three seasons. Women’s Professional Soccer started play in 2009 and also lasted only three seasons.

NWSL took the field in 2013 and has a management contract with the U.S. Soccer Federation, which has listed nearly $8.5 million as expenses attributable to the league. The USSF pays the salaries of 22 allocated national team players, providing the NWSL a subsidy and the ability to market the top American players.

NWSL launched in 2013 with eight teams, increased to nine the following season and 10 in 2016, then went back to nine in 2018 — of which four share owners with MLS.