Ledecky rallied to beat Danish Olympian Lotte Friis by more than a body length in 8 minutes, 26.70 seconds. Friis, who led the first 600 meters, took second in 8:28.65. Savannah King was third at 8:39.87.
Ledecky finished fourth in the 200 individual medley shortly before she stepped on the blocks for the 800 at the University of Texas.
"I swam the 200 IM this morning just for fun," she said. "I swam it, and did pretty well, so I swam it tonight as a challenge, just for something fun and different to do. I'm not sure I'd ever do it again, but in January, there's nothing to lose."
Olympian Jessica Hardy won the 100 breaststroke by about a body-length, holding off Laura Sogar over the final 10 meters with a time of 1:07.05. Sogar was second in 1:07.76. Katie Meili was third.
Olympic champion Yannick Agnel of France won his third event, taking the 1,500 freestyle in 15:07.76. Michael McBroom was second in 15:16.72. Ous Mellouli of Tunisia, the 2008 Olympic champion, was third in 15:19.09.
In the 100 backstroke, reigning Olympic champion Matt Grevers won in 53.72. Arkady Vyatchanin of Russia was second and Ryan Murphy was third.
In other races, Caitlin Leverenz led all the way to win the 200 individual medley; Olympian Conor Dwyer won the men's 200 IM; Canadian Audrey LaCroix won the 200 butterfly; Ross Murdoch of Britain won his second event of the meet, taking the 100 breast; Canadian Hillary Caldwell completed a sweep of the backstroke events with a win in the 100; Tom Luchsinger won the 200 butterfly.