I was able to squeeze in one more Half for the year by adding Wichita in September. I'm still going to keep July off (a month that will be spent mostly at the beach) as well as December.
The Johnston's Half Marathon is the weekend of September 15.
My updated 2013 calendar:
June 22 - Seattle, Washington
July - off
August 25 - Tenants Harbor, Maine
September 15 - Wichita, Kansas
October 27 - St. Louis, Missouri
November 9 - Savannah, Georgia
December - off
With Kansas now added to the calendar I'm on track to closing 2013 with 26 races/states completed for the challenge.