Spain have become the first country since the United States 14 years ago to top the WTA and ATP rankings at the same time.
While Rafael Nadal is predictably keeping the number one spot in the men's rankings, Garbine Muguruza made her debut at No. 1 on Monday.
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America's, Andre Agassi and Serena Williams are the only other compatriots to top the rankings at the same time; both No. 1 in 2003.
Muguruza, the Wimbledon champion in July, rose two spots from No. 3 after getting to the fourth round at Flushing Meadows for the first time. She is the 24th woman to lead the WTA since it introduced computer rankings in 1975 - and the second Spaniard, after Arantxa Sanchez Vicario.
Nadal remained at No. 1 by winning his second Grand Slam trophy of the season and 16th of his career with a 6-3, 6-3, 6-4 victory over Kevin Anderson in the final at Flushing Meadows on Sunday.
The man, who won the year's other two major titles, Roger Federer, moved up one place to No. 2.
Anderson went from 32nd to 17th by reaching his first Grand Slam final. He was the lowest-ranked US Open men's finalist since the ATP computer rankings began 44 years ago.