1. Amy Olson had a day to remember in Houston: not only did she tie her lowest career opening-round score in a major championship (67), she also made the 29th hole-in-one in US Women’s Open history. Olson is the first player to shoot in the 60s in a round with a hole-in-one at this championship since Susie Redman in the opening round in 1997. This is Olson’s lowest career round in the US Women’s Open by two strokes.

2. Olson wasn’t the only player to make an ace on Thursday – Yu Jin Sung also made one, hers coming on the 169-yard 4th hole at Cypress Creek. This marked the first time since 1983 that there were multiple aces made in the same round of the US Women’s Open. In the third round that year, Pat Bradley and Jane Lock each made holes-in-one at Cedar Ridge Country Club in Broken Arrow, Okla.

3. Olson is the first American player to lead the US Women’s Open outright after Round 1 since Stacy Lewis held a one-stroke lead at Pinehurst six years ago. Since 1990, only four women have held the opening-round lead at this championship and gone on to win: Patty Sheehan in 1992, Juli Inkster in 2002, Annika Sorenstam in 2006 and Ariya Jutanugarn in 2018.

4. On Day 1, Cypress Creek played as the more difficult of the two courses, averaging 1.1 strokes more than its counterpart, Jackrabbit. Fifteen of the 23 rounds under par on Thursday came on the Jackrabbit Course, which yielded a higher percentage of greens in regulation and fewer putts per green. Jackrabbit also saw 37 more birdies than Cypress Creek did in the opening round.

5. Moriya Jutanugarn opened with 68, the sixth time in her major-championship career she has started with a score of 68 or lower. Jutanugarn will look to reverse a scoring trend that has hampered her in majors: since 2013, she has a scoring average of 71.3 in the opening round of majors. In Rounds 2 through 4, that average jumps a full stroke to 72.3. When comparing the scores to par, it’s staggering: Jutanugarn is 10 under in Round 1, but 68 over par the rest of the week.

6. Defending champion Jeongeun Lee6 shot 73, making just one birdie along the way. No defending champion has finished in the top 10 at the US Women’s Open since Juli Inkster finished eighth in 2003. That was also the last time that the defending champion opened her week with a round in the 60s (Inkster shot 69). The last player to win this championship in back-to-back years was Karrie Webb in 2001 and 2002.

7. Lexi Thompson struggled on the greens at Cypress Creek Thursday, needing 34 putts in her opening-round 74. She averaged 2.08 putts per green in regulation Thursday, tied for 129th in the field. Thompson sits seven shots back of the lead – since 1990, the largest opening-round deficit faced by an eventual winner was seven strokes, done on two occasions (Meg Mallon in 2004 and Sung Hyun Park in 2017). Amazingly, despite all her success in this championship, Thompson has never started the US Women’s Open with a round in the 60s in 14 starts.

8. Speaking of Sung Hyun Park, the 2017 champion was throwing darts Thursday at Jackrabbit: her average proximity to the hole was 14 feet, 1 inch on Thursday, nearly 2½ feet better than any other player in the field. Park entered the week ranked third in strokes gained total per round in the US Women’s Open since 2015. She opened with a 1-under-par round of 70 on Thursday.

9. After a poor start, Carlota Ciganda finished on a tear in her opening round, making birdie on four of her last six holes to finish at even-par 71. Ciganda leads all players in cumulative score to par (-12) and strokes gained total at the US Women’s Open since 2017. Ciganda hit seven straight greens in regulation to finish her first round.

10. Twenty-five of the last 30 US Women’s Open champions were at or within five strokes after the opening round. Eight of the last 11 winners were inside the top 10 after Day 1. Only four of the 30 winners since 1990 shot 73 or higher in the first round of the championship.

- Justin Ray, USGA