Not Legal Advice: In Iowa, the laws are a little more specific, which means depending on where the crack is and how bad it is, you could get ticketed for the damaged windshield. Many states actually have laws that allow police officers to ticket cars with cracks in the "critical area" of the windshield, which is the area that is covered by the windshield wipers, particularly on the driver's side area.
Of interest, statistics in the past showed that nearly 8 out of 10 auto glass replacements fail to be installed properly and safely. On November 10, 1903, Mary Anderson patented the windshield wiper. On this date, the patent office awarded US Patent No. 743,801 to Anderson.
In windshield related news, sadly, a deer crashed through the windshield of a public bus that was being driven in Johnstown, about 65 miles east of Pittsburgh, Pennsylvania. Authorities say that the driver stopped the bus and opened the door and the deer walked through the door and off the bus. According to statistics from State Farm insurance, an estimated 1.5 million vehicles collide with deer every year in the United States, causing $1.1 billion in property damage.