McIlroy missed the cut the last time the US Open was held at Oakmont in 2016
Rory McIlroy found Oakmont Country Club a bruising challenge as only five players from round one's morning wave ended under par at the US Open.
Masters champion McIlroy had started well and was two under through nine holes, but then unravelled with four bogeys and a double bogey as he posted a four-over 74.
JJ Spaun, who McIlroy beat in a play-off to win The Players Championship in March, leads the way on four under. The American had four birdies in his opening eight holes and his is the only bogey-free round halfway through day one.
South Africa's Thriston Lawrence is one behind Spaun after taking 67 shots on the notoriously difficult Pennsylvania course which is hosting a record-extending 10th US Open.
