Marathon of photos: Twitter and Instagram images from the 2013 Chicago Marathon

Amtrak Police has at least 8 officers and two dogs on Canal outside Union Station #ChicagoMarathon pic.twitter.com/M1wuYiXo7J

— Diana Novak Jones (@dhnovak) October 13, 2013

US Marshals at Madison and Franklin, say they've stepped up presence at marathons since Boston #ChicagoMarathon pic.twitter.com/g2uNE3GQZe

— Diana Novak Jones (@dhnovak) October 13, 2013

It goes from so loud to silent so fast. #ChicagoMarathon pic.twitter.com/aSJmgWO3tQ

— Diana Novak Jones (@dhnovak) October 13, 2013

Quick stop for a hug 1.5 miles in #ChicagoMarathon pic.twitter.com/eHggpVre1a

— Diana Novak Jones (@dhnovak) October 13, 2013

Signs of the marathon: Those head signs (a la NCAA fans) are popular this year #ChicagoMarathon pic.twitter.com/m9gw2WkSf7

— Diana Novak Jones (@dhnovak) October 13, 2013

Great #ChicagoMarathon signs at Washington and La Salle. @redlineproject pic.twitter.com/xWviFmjIxy

— Alexandra Trumbull (@atrumbull) October 13, 2013

Signs of the #ChicagoMarathon pic.twitter.com/heFVvKOWVw

— Diana Novak Jones (@dhnovak) October 13, 2013

These bomb sniffing dogs were flown in (along with their handlers) from NY. Hanna and Parnell hard at work pic.twitter.com/WHoBQqeiNK

— Diana Novak Jones (@dhnovak) October 13, 2013

#ChicagoMarathon!! @redlineproject pic.twitter.com/ueerrAj58H

— Alexandra Trumbull (@atrumbull) October 13, 2013

30-second moment of silence at the start of the #chicagomarathon for the victims of the #Boston Marathon terrorist attacks. #chimarathon

— The Red Line Project (@redlineproject) October 13, 2013

Thanks to @photojeskos for letting me rock the @SunTimes camera today for all 26.2 miles. This will be fun, I promise. @ChiMarathon #CM13

— LeftHash (@LeftHash) October 13, 2013