The Metro East has grown steadily over the past decade, with more people living in seven of the eight counties than in 2000.

Monroe County, with just under 33,000 people, is one of the fastest-growing areas in the state, on pace with several collar counties of Chicago, which remains by far the largest city in Illinois. But it has shrunk by nearly 7 percent.

The Census Bureau released on Tuesday detailed population numbers for Illinois, along with three other states. So far, figures for 12 states have been released since the beginning of the month. The Census Bureau has not given an exact date for Missouri's data. By law, all state population numbers down to city blocks must be released by the end of March, as states grapple with redrawing congressional districts.

In December, the Census Bureau released state-level population numbers, which showed gains in both Illinois and Missouri since 2000, but at a much slower rate than many states in the South and the West. As a result, both states lost a congressional seat.

Based on the census numbers released Tuesday, Madison and St. Clair counties remain among the 10 largest in the state, but they swapped positions from 10 years ago. St. Clair County is ranked eighth with 270,056 people — 774 more residents than Madison County, at ninth.

"After a decade slump, I'm very happy we're showing some growth," said Terry Beach, St. Clair County's economic development director.

Despite the Metro East's size, it has none of the 20 largest cities in Illinois. The largest, Belleville, stands at 44,478.

The other Metro East counties that grew over the decade include Bond, Calhoun, Clinton and Jersey. Only Macoupin County dropped in population.

The gain in St. Clair County is significant in that it reverses a population decline from 1990 to 2000 and does so as its once biggest city, East St. Louis, continues a skid, dropping 14 percent, to below 30,000 residents.

The largest gain comes in O'Fallon, which saw its population jump by 29 percent, becoming the third-largest city in the Metro East. Ten years ago, it was ranked sixth. It surpasses East St. Louis, Alton and Collinsville. Granite City lost population but moved from third to second.

"We're not surprised," said O'Fallon city administrator Walter Denton. "We did special censuses in 2005 and 2008, so we knew we were growing."

But Denton thought the population would be closer to 30,000. The official census number is 28,281, up from 21,910.

In Illinois, 10 percent of income tax is redistributed to cities based on population. O'Fallon wanted to make sure it was getting its fair share and had the official counts done, Denton said.

Monroe County officials also were optimistic that the census information would show population gains in their part of the region. At 19 percent, it ranks sixth among all Illinois counties with the highest percentage of growth. The five ranking higher than the small Metro East county are all suburbs of Chicago.

County officials attribute the growth to a migration of residents from south St. Louis County — a short drive over the Jefferson Barracks Bridge — as well as St. Clair and Madison counties, which both grew but at a slower rate, with increases of 5.5 percent and 4 percent, respectively.

Monroe County Board Chairman Delbert Wittenauer said the county's simpler life and quality schools drew families to his part of the region.

"We're more family oriented than a lot of places. The general population goes to church, goes to school, goes to community events," Wittenauer said. "Our community, if you are in need of something, there are people here who are willing to help. It's a real team effort down here."

Another draw is the affordable housing, said Monroe County Assessor Carl Wuertz. First-time home buyers can find a nice place to buy for about $100,000, he said.

St. Clair County leaders also were happy with the census results, saying that campaigns to get people to fill out their census forms had apparently paid off.

"I kind of expected more," said Charles Kofron, census liaison for St. Clair County. "We focused on hard-to-reach populations. We had a very aggressive complete count campaign."

St. Clair County benefited from the continued growth of Scott Air Force Base, the largest employer in the Metro East with more than 14,000 military and civilian jobs. Cities such as O'Fallon, Fairview Heights, Shiloh, Swansea and Mascoutah have seen their populations grow, in large part, because of the base.

"The numbers are very pleasing to us," said Beach, the county's economic development director. "It shows southwestern Illinois continues to be 25 percent of the St. Louis region and growing."