The Amish are one of the fastest-growing religious groups in North America, according to a new census by researchers at Ohio State University.

The study, released July 27 at the annual meeting of the Rural Sociological Society, reports that a new Amish community sprouts up about every three and a half weeks. Nearly 250,000 Amish live in the U.S. and Canada, and the population is expected to exceed 1 million around 2050.

The growth may not be visible outside Amish country, but the rural settlements definitely see the boom. “This place has grown,” said Daniel Miller, 52, who has spent his life on an Amish settlement. “It’s because of all of the kids.”