The 10 mile course took runners from the starting line outside Soldier Field, along the lake front path, through the Bear’s tunnel.
About 45,000 marathoners hit the streets of Chicago Sunday morning to complete a personal goal.
The Bank of America Chicago Marathon began downtown.
The 26.2-mile course snakes through 29 neighborhoods, including Lincoln Park and Pilsen. Race organizers say morning temperatures are expected in the upper 50s. Afternoon temperatures are expected in the mid to upper 70s.
Organizers say they're prepared for higher-than-normal temperatures. In 2007, the race was shut down early amid unusually hot and humid conditions. Officials aren't sweating too much over warmer-than-usual forecasts for Sunday's race because they believe they're equipped to handle the heat.
Temperatures are expected to approach 80 degrees, the fourth time in five years the weather has been unusually warm, but medical director Dr. George Chiampas says a team of more than 1,400 medical volunteers has "been tested."
A Michigan man with a heart condition died four years ago, but since then, race officials have improved communication between various agencies and runners. They've also added more water distribution points and medical aid stations.
Participants represent all 50 states and more than 100 countries.
Two-time defending champion Shobukhova of Russia will try to become the first three-peat winner in the race's history. And Ryan Hall will try to become the first American to win a major since the New York City Marathon in 2009.
Gov. Pat Quinn will hold the finish line tape.