Texas added almost 4 gigawatts and Iowa installed 1.7 gigawatts, expanding their lead in wind power capacity, according to a report from the American Wind Energy Association released Wednesday. That helped boost total U.S. installations to 9.1 gigawatts last year, the most since the expiration of federal tax credits triggered a building boom in 2012.

Those tax credits got extended several times and were set to expire again this year, setting off another race to complete projects. That ushered in the industry’s third-best year in history, and another extension for one year was approved just before they expired.