In all, 8,300 more people left Wyoming than moved to the state over the past year but new births meant that the total loss of population was less than that.
It showed Connecticut's population in 2017 is estimated at 3,588,184.
By comparison, Missouri's population stands at 6.1 million, an increase of 124,607 people since 2010.
Different states in the West - Nevada, Utah and Washington - saw comparative rate increments in their populace.
The U.S. population grew by 2.3 million between July 1, 2016, and July 1, 2017, representing a 0.72 percent increase to 325.7 million.
"Rural counties and downstate IL have taken the brunt of population declines in the past, but the number of people in Chicago, which has propped up the state, has leveled off", Harger said.
U.S. Census estimates released Wednesday showed Pennsylvania rose a notch to become the fifth-most populous state, passing a shrinking IL by about 3,500 people. In 2017, 38.0 percent of the nation's population lived in the South and 23.8 percent lived in the West.
The population figures are closely watched as a sign of what will happen when congressional maps are redrawn after the 2020 Census. The number of voting-age Americans grew to 252.1 million - a near 1 percent increase over the year.
Illinois' population fell by 33,703 people to just over 12.8 million, according to the estimates.
The division's release was based on data collected by the United States Census.
ME grew 4 percent, Rhode Island by 2 percent, and CT and Vermont basically broke even.
The world population was listed at more than 1.44 billion, with China, India, the U.S., Indonesia, Brazil, Pakistan, Nigeria, Bangladesh, Russia and Japan making up the top 10 most populous countries, in order.
However, net worldwide migration decreased 1.8 percent - the first drop since 2012 to 2013.
"Domestic migration drove change in the two fastest-growing states, Idaho and Nevada, while an excess of births over deaths played a major part in the growth of the third fastest-growing state, Utah", said Luke Rogers, chief of the bureau's Population Estimates Branch.