Serena Williams going for the single-season Grand Slam has tennis fans so excited that, for what is believed to be the first time in US Open history, the women's singles final sold out before the men's single final.

USTA spokesman Chris Widmaier said ticket records, as with anything, are less reliable over time, but the organization is confident that this is the first time the ticket demand was greater for a women's final.

In fact, in some years, the women's final has not even sold out.

Widmaier said that USTA data suggests that seats are trading at three times the value they usually do.

Ticket resale market tracker TiqIQ says the average listed price on the resale market for the women's final is now $859, versus a men's final average resale ticket price of $897. That $38 difference in resale prices is remarkable considering TiqIQ says the smallest difference in price between the men's and women's finals was in 2012, when the average ticket price for the men's final was $150 more than for the women's final.

If Williams wins the US Open, which begins Monday, she would be the first woman to win all four Grand Slams in a single season since Steffi Graf did it in 1988. With a US Open singles title, she would also tie Graf for second place all time for Slams singles titles at 22. Margaret Court is first with 24.

The women's singles final is on Saturday, Sept. 12; the men's singles final is Sunday, Sept. 13.