According to the American Wind Energy Association, in 2007 Iowa was the only state to have more than 5% of its electricity provided by wind. It now has over 5GW of installed capacity, and is the state sourcing the highest proportion of electricity from wind, at 24.5%.
However, these figures do not tell the whole story. It is interesting that a state like South Dakota, which has only 784MW installed and did not install any capacity last year, sources almost a quarter of its electricity from wind. This can be attributed to its low demand due to a small industrial base and small population.
It is worth noting that these statistics count megawatt hours generated in a state as being used by that state. In a state such as California, which may be importing wind, these totals are lower than the total renewables used.