Ariya and Moriya Jutanugarn combined for an 11-under 59 Thursday to take the second-round lead at the Dow Great Lakes Bay Invitational, an LPGA Tour team event at Midland Country Club in Midland, Michigan.
Playing the round under a best-ball format, the sisters made six birdies on the front nine and five more on the back, including No. 18, to score golf's hallowed number.
In the tournament's debutant year in 2019, one round of 58 and one 59 were scored during best ball, so Thursday's will not be counted as an official 59. Annika Sorenstam is responsible for the LPGA's only stroke-play 59 at a tournament in 2001.
That won't stop the accomplished LPGA veterans from celebrating for now. The Jutanugarns moved to 14 under for a two-stroke lead over the tandem of India's Aditi Ashok and Thailand's Pajaree Anannarukarn. Tied for third at 11 under were South Koreans Mi Jung Hur and Jeongeun Lee6 (62 Thursday) and Thai teammates Wichanee Meechai and Pavarisa Yoktuan (63).
The best-ball format led to a number of other low scores. Chinese Taipei teammates Wei-Ling Hsu and Min Lee posted a 10-under 60. Four teams carded a 61: South Korea's Haeji Kang and Amy Yang; fellow South Koreans Eun-Hee Ji and Hyo Joo Kim; Brittany Altomare and Angel Yin; and Jennifer Chang and Kristen Gillman.
The field played alternate shot for the first round, and Friday's third round will be the same before best ball returns in the final round.
First-round co-leaders Nelly and Jessica Korda only managed a 69 Friday and dropped out of the top 20 as a result.