Kastor runs 1:11:38 to set new U.S. 40-and-older mark.
Christo Landry won the men's USA title in 46:41.
Kenyan women sweep top five positions; Kipsang's win leads men's team to silver medal.
Marc Davis' mark of 13:24 has stood since 1996.
Lauren Kleppin and Tyler Pennel will compete in Saturday’s World Half Marathon Championships in Copenhagen.
Planning and organizing a race is a much bigger challenge than it first seems, writes Daniel Seidel.
The 10-time global medalist will make his debut at the "World's Fastest 5K" at the end of March.
Shalane Flanagan, Molly Huddle and Emily Infeld will lead the way in the inaugural event.
Be sure to do both general and specific warm-up activities before races and faster workouts.