The latest census into religion in the US has revealed a dramatic increase in the number of Latter-day Saints, or Mormons, and Muslims, a modest increase in the number of evangelical Protestants, and a drop in the number of Catholics and mainline Protestants.

Muslims saw the greatest growth rate among the five main religious groups studied by the Association of Statisticians of American Religious Bodies (ASARB).

Their numbers increased by 66.7 per cent in the 2010 census from a decade earlier. Latter-day Saints saw the next highest growth at 45.5 per cent, followed by evangelical Protestants at only 1.7 per cent. The number of Catholics decreased by five per cent and the number of mainline Protestants decreased by 12.8 per cent.

Notably, when combined, nondenominational and independent churches are now the largest faith group, with over 12 million adherents, according to the report.

Evangelical Protestants and Latter-day Saints saw their greatest growth in the nine most populated metropolitan areas. These areas each have over 5 million people. Evangelical Christians increased their numbers by 12.3 per cent and Latter-day Saints increased their numbers by 66.9 per cent in these areas. Muslims, by contrast, grew at a faster rate outside of the major metropolitan areas.

The census also shows an increase in religious diversity in the United States. In the 2000 census, at least one non-Christian religious congregation was found in 21 per cent of America's counties. In the 2010 census, that had risen to 31 per cent, a nearly 50 per cent increase.

ASARB's US Religion Census is the most thorough study of its kind. County-level data is collected for 236 different religious groups. The first census was taken in 1952 and followed up roughly every 10 years.

"With 236 participating bodies, the 2010 US Religion Census is the most comprehensive local-level analysis of US religious adherents and attendance in more than 60 years," said Clifford Grammich, the chairman of the ASARB operations committee for the study. "We are especially pleased to have increased participation for several independent and non-Christian bodies."