More than 177,000 Houston residents have signed up for health insurance through the federal marketplace, far exceeding expectations for the city.

According to an email obtained by The Associated Press, as of April 5 177,825 Houston residents enrolled for insurance under President Barack Obama's signature law. The email was written by Marjorie McColl Petty, the regional director for the U.S. Department of Health and Human Services in Dallas.

The expectation had been that 138,000 Houston residents would sign up. Petty told Houston officials the numbers reflect a successful 13-county regional effort.

These are the first enrollment figures for Texas, where one in four are uninsured, the highest rate in the nation. The state is considered crucial to the Affordable Care Act's overall success, but enrollment had lagged in February.