"Even coming from a mountainous area, this was still really hard," Krah said in a statement after winning. "It was just an endless assault of hills."
Devon Crosby-Helms, 30, of San Anselmo, finished first among the women with a time of 2 hours 44 minutes 5 seconds, according to results.
"That was extremely satisfying," Crosby-Helms said in a statement.
"This was my third time racing here, and I really felt I had a good chance to win."
More than 7,000 runners took part in this year's marathon, alongside 18,000 people who participated in two separate half marathons, a 5K run and a Munchkins Kids Fun Run, organizers said.