These are some new (scary) statistics from The Autism Autoimmunity Project (TAAP). I have reported the states with the highest percent of increase.

Number of cases (for ages 3-5) reported in:
2003-2004; 2004-2005; and the percent increase:
North Dakota: 20 32 60%.

Montana: 23 32 47.6%

New Hampshire: 82 120 46.3%

Arizona: 157 223 42%

According to this study, possible causes for the increase in autism are: autoimmunity issues, the MMR vaccine, other vaccinations, and environmental factors. The state with the highest number of reported cases in 2004-2005 is California with 22,691 cases.