World record-holder Katie Ledecky booked her place at the World Swimming Championship on Tuesday with a women's 800-meter freestyle victory on the opening day of the US national championships at Indianapolis.
Nine-time Olympic champion Ledecky, who has won 800 free gold at the past four Olympics and 1,500 free gold in the past two, is a 21-time long course world champion and captured her 31st US crown by taking the 800 in 8mins, 5.76secs.
Claire Weinstein was a distant second in 8:19.67.
The top two finishers in each event plus relay swimmers in the 100m and 200m freestyles will make the US team for the worlds in Singapore from July 11-August 3 provided they meet qualifying time standards up to a maximum of 26 men and women.
Ledecky is expected to swim the 200, 400 and 1,500 freestyles later in the meet, which continues through Saturday at Indiana University Natatorium.
A month ago at the US swim series event in Fort Lauderdale, Florida, Ledecky swam the second-fastest 1 500 freestyle in history, her second-best 400 time and a new 800 free world record of 8:04.12.
Bobby Finke, who set the men's 1,500 world record of 14:30.67 to defend Olympic gold at Paris, won the US 1 500m crown in 14:48.65.
Three-time Olympic medalist Torri Huske won the women's 100 free in 52.43, .35 ahead of four-time Olympic medalist Gretchen Walsh, while Jack Alexy, a member of the US 4x100 free relay champions, won the men's 100 freestyle in 47.17 with Patrick Sammon second, .30 adrift.
Caroline Bricker took the women's 200 butterfly in 2:05.80 with eight-time Olympic medalist Regan Smith second, .05 back.