June 19 (Reuters) - Katie Ledecky completed her Tokyo Games to-do list with a win in the 800 metres freestyle at the U.S. Olympic swimming trials on Saturday and heads to Japan ready to defend her three Rio gold medals and make history in the 1,500. A commanding win in the 800 free capped a businesslike week in the Omaha pool for the 24-year-old American. She failed to deliver the times some had expected but got the job done, qualifying in four individual events the 200, 400, 800 and 1,500, which will be contested by the women for the first time at the Olympics. "It"s been fine. I haven"t been super happy with my times but still feel like I"m in a good spot," Ledecky told reporters after the trials. "Mission accomplished." "It"s not easy to get through the yardage I got through this week. It was good to just do it and get the job done, check the box move forward and not get too caught up in times." The gold medal winner in the 800 at the 2012 London and 2016 Rio Olympics, Ledecky has ruled over the event for nearly a decade, posting the top 23 times of all time. There was never a moment on Saturday when that domination was in doubt as Ledecky left the field in her wake powering to victory in a time of eight minutes, 14.62 seconds - almost six seconds clear of 15-year-old Katie Grimes, who also earned a ticket to Tokyo with her second-place result. While it was business as usual for Ledecky, the evening also provided a major upset when Regan Smith, the 200-metres backstroke world record holder, finished third. She will not race the event in Tokyo. Smith had not been in top form coming into the meet but was still expected to grab one of the two spots. Instead it was Rhyan White getting to wall first in 2:05.73 ahead of Phoebe Bacon. Smith, however, had already secured her ticket to Tokyo with a win early in the 100 back. There were no slip-ups in the men"s 100 butterfly, where world record holder Caeleb Dressel powered his way to a commanding win ahead of Tom Shields. After flirting with his own world mark of 49.50 in the preliminaries and semifinals, Dressel was expected to attack the record, but without being pushed he won in a time of 49.87. Dressel has now qualified in two individual events - the 100 butterfly and 100 freestyle - and is likely to add third to his work load in Japan after posting the top time of 21.51 seconds in the 50 freestyle semifinals.