Day 1 of the 2021 U.S. Open at Torrey Pines Golf Course in San Diego is in the books.

Round 1 is not over, though.

A 90-minute fog delay pushed the beginning of the tournament back. Thirty-six golfers were on the course when the day's action was suspended for darkness, so the first round will conclude early Friday morning before Round 2 can begin.

Louis Oosthuizen and Russell Henley sit atop the leaderboard at four under.

Oosthuizen caught fire during his round, knocking home birdies on Nos. 16-18. The putter cooperated, and he drilled an 18'11" putt on No. 16:

A 11'2" putt on No. 5 tied him with Henley:

Oosthuizen may have never won a U.S. Open, but he's been brilliant at the major with four top-nine finishes. Justin Ray of Twenty First Group provided some stats:

Oosthuizen did not finish his round, and he currently sits on the No. 8 green. He has about 12 yards for a birdie.

Henley entered the clubhouse as the tournament leader thanks to a four-under 67. Six birdies helped him emerge in first place, and he can thank his exceptional putting (fourth in strokes gained on the green).

Torrey Pines hasn't exactly been kind to Henley in the past, as he told Jason Sobel on SiriusXM Radio following his round:

But he was all smiles Thursday thanks to a fantastic short game.

It's awfully crowded at the top, though, and some of golf's best players are in the mix.

It's never a good sign for the competition when four-time major winner Brooks Koepka is lurking around, but that's the case as he finished the day two under.

Koepka was four under at one point after knocking home this birdie on No. 12:

A pair of bogeys knocked him down to two under, but he's certainly off to a great start.

It's been an eventual few weeks for another contender in Jon Rahm. The Spaniard was forced to withdraw from the Memorial Tournament after testing positive for COVID-19. He was leading the tournament by six strokes at 18 under going into Sunday.

That was undoubtedly disappointing, but he's recovered and in great form, shooting two under on Thursday. This 30-feet birdie putt on No. 14 helped matters.

Masters champion Hideki Matsuyama is seeking his second major win of the year, and he's in good shape to do so at two under. He had three birdies and just one bogey.

Other notable contenders include 2019 Open champion Francesco Molinari (three under) and Xander Schauffele (two under).

On the flip side, a who's who of golf's biggest names sit below the one-over cut line going into Friday.

World No. 2 Justin Thomas is at two over. He started the day with 11 straight pars before bogeying No. 3.

He bogeyed No. 5 as well but came through with a clutch birdie on the tough par-four sixth (519 yards).

Thomas did finish with one more bogey but ended the day just one shot below the cut line, so he could very well end up playing this weekend despite his current position.

Three-time major winner Jordan Spieth is also on the outside looking into the picture at six over. He was treading water through 14 holes at two over, but a disastrous finish, which included a double bogey on No. 6, led to the six-over day.

It wasn't been a good day for former U.S. Open champions. Gary Woodland, the 2019 victor, is three over. He was one under through 10 holes but carded five bogeys from Nos. 11-17 before finishing with a birdie on the last.

Bryson DeChambeau, who was the only player to shoot under par in 2020, shot two over. His approach game didn't do him any favors, as he finished 127th in strokes gained.

PGA Championship winner Phil Mickelson's quest to win that elusive U.S. Open did not get off to a good start, as he's four over. The six-time major winner is still basking in the glow of his Wanamaker Trophy, though.

Justin Rose, the 2013 U.S. Open champion, had three straight bogeys from holes Nos. 4-6 to fall below the cut line. He has seven bogeys and zero birdies through 17 holes.

Webb Simpson, who won the U.S. Open the year before Rose, had a day to forget and finished eight over. Six bogeys on the front nine and a double bogey on No. 17 have all but sent Simpson home early.

All statistics via U.S. Open website.