Besides which, some states may have very cheap land, but property taxes are incredibly high. For example, you might be able to find some cheap, rural land in Oregon, but you will end up paying 5-10% of it's value each and every year (for eternity) in property taxes.
When you factor in the taxes, as well as the fact that you will probably have to pay interest on the taxes (which are generally bundled with your mortgage payments over a 30 year period), even cheap land in California ends-up looking like a bargain by comparison.
Look for a combination of not only inexpensive land values, but inexpensive land taxes, living expenses and other local taxes, permits, fees, etc. Some of the areas that have tended to be better all-around values in recent years are Texas, North/South Dakota, Louisiana and Wyoming. Stay away from any state with deep financial problems. Eventually, they will be reaching into your pocket to solve their fiscal problems.