With a little luck you and 4,000 of your closest running buddies will participate in Sacramento’s largest half marathon! There’s no need to have Irish blood running in your veins to participate in the Shamrock’n half marathon but you will need to register soon; we’re over 80% full. Save some green if you register by March 15. The Shamrock'n Half Marathon has become one of Sacramento's must-do events. The event features flat, fast courses with scenic Sacramento River views and a great finish on Raley Field.