It was the ideal early birthday present for Phelps, who turns 31 tomorrow.
The 18-time Olympic champion had looked in fine form in the semi-finals yesterday when he finished over a second clear of his nearest challenger Pace Clark at the CenturyLink Center.
It was, therefore, no surprise when Phelps touched home victorious in the final in a time of 1min 54.84sec to secure his Rio 2016 spot, with Tom Shields touching home in 1:55.81 to claim the second place.
After sealing his place in the team, Phelps will now turn his attentions to reclaiming the Olympic title he won at both Athens 2004 and Beijing 2008.
He had been surprisingly beaten by South Africa’s Chad Le Clos at London 2012.
Missy Franklin was hoping to earn a women’s 200m freestyle spot, having failed to qualify yesterday for the 100m backstroke, one of her four gold medal winning events from London 2012.
The 21-year-old clocked a time of 1:56.18 to earn second place in the event behind the dominant Katie Ledecky, who won in 1:54.88.
Both Franklin and Ledecky are now due to compete in 200m and 800m freestyle relay events at the Games, the latter having already secured a place in the individual 400m freestyle competition.
Leah Smith and Allison Schmitt finished in times of 1:56.63 and 1:56.72 to earn places in the American 4x200m relay team at the Games.
After booking her place in the women’s 400m individual medley competition on the first day of the trails, Maya DiRado was able to add the shorter 200m race to her schedule at Rio 2016.
The 23-year-old eased to victory in a time of 2:09.54, the third fastest in the world this year, to seal the place.
Melanie Margalis looks likely to take the second spot on offer after finishing in 2:10.11, following a head-to-head battle with Caitlin Leverenz, who finished third in 2:10.16.
Tomorrow places are due to be decided in the men's 200m,breaststroke and 100m individual medley and women's 100m butterfly.