More than 61 million immigrants and their U.S.-born children under the age of 18 now reside in the United States, according to a new Center for Immigration Studies analysis of U.S. Census Bureau data.

The CIS report estimates that of the 61 million total, three-fourths or 45.3 million, are legal immigrants and their children. The remaining 15.7 million are illegal immigrants and their children.

According to CIS, the current ratio of nearly one in five U.S. residents either immigrants or the children of immigrants is “a complete break with the recent history of the United States”

“As recently as 1970, there were only 13.5 million immigrants and their young children in the country, accounting for one in 15 U.S. residents,” the report reads, noting that since year 2000 alone, the population of immigrants and their minor children increased by 18.4 million people.

Additionally, the report highlights that the immigrant population in the U.S. has grown six times faster in that past 45 year than the total population of the U.S. According to CIS from 1970 to 2015 the immigrant and their children population grew by 353 percent compared to the nation’s 59 percent population growth.

The growth has CIS questioning the nation’s ability to absorb the high level of new arrivals.

“These numbers raise profound questions that are seldom even asked: What number of immigrants can be assimilated? What is the absorption capacity of our schools, health care system, infrastructure, and labor market? What is the effect on the environment and quality of life from significantly increasing the nation’s population density?” Steven Camarota, CIS’ Director of Research, said Monday in a statement.

In his report, Camarota further breaks down the data by state, noting that the growth in population of immigrants and their children since 1970 “as been nothing short of astonishing.” Many of the states he highlighted with high immigrant and their minor children population growth are located in the south — including Georgia, Nevada, North Carolina, Arkansas, Tennessee, Virginia, Oklahoma, Texas and Arizona.

“With 45 million legal immigrants and their young children already here, does it make sense to continue admitting more than one million new legal permanent immigrants every year?” Camarota added.

Camarota’s state findings included: