Sun Belt cities such as Houston, San Antonio and Phoenix have grown substantially in recent years, but migration is only part of the reason. Those communities also have reached out to annex thousands of their neighbors.
Annexation, in addition to population flow, has been an important factor in the growth of dozens of cities, primarily in the South and West, the Census Bureau's Joel Miller reports in American Demographics magazine.
The report said that annexation not only adds population, but it increases prestige and, perhaps most importantly, tax revenues.
Houston grew more than 29% from 1.2 million to 1.6 million people between 1970 and 1980. The Texas city is often cited in studies of the attraction of the Sun Belt to outsiders.
"But the city also annexed (more than 200,000) people," Miller said. "Without the annexation, the city would have grown only modestly."
While Houston was by far the biggest gainer through annexation, Charlotte, N.C., was second, adding 84,700 people during the 1970s.
Indeed, Charlotte, Chattanooga, Tenn., which annexed 53,800; and Savannah, Ga., which added 35,300, would not have have grown at all during the decade without annexation.
And while such expansion didn't change the comparative number of people in each region of the country, annexations did make Southern and Western cities seem to grow faster than those in the Northeast.
Rare in North
"Annexation is rare in New England and the Middle Atlantic states. In all of New England, there were only four trivial annexations in the 1970s. The Middle Atlantic states added only 37 square miles and an estimated 9,000 people to places through annexation," Miller said.
Cities in Southern states were more likely to annex suburbs. In addition to Charlotte, Savannah and Chattanooga, for example, Lexington, Ky., added 75% to its population in the 1970s; Baton Rouge, La., added 30%, and Lynchburg, Va., 26%.
Other strong gainers that used annexation were Roanoke, Va.; Gainesville, Fla.; Owensboro, Ky.; Montgomery, Ala.; Jackson, Miss.; Little Rock, Ark., and San Antonio and Port Arthur, Tex.
In the Middle West, Miller reported, Champaign, Ill., and Muncie, Ind., used annexation to add between 10% and 25% of their 1970 population. In the West, annexations made similar increases in Colorado Springs, Colo.; Albuquerque, N.M.; Mesa, Ariz., and Carson, Calif.
Four States Lead Way
Overall, California, Florida, Illinois and Texas accounted for 40% of all annexations in the decade.
In North Dakota and Wyoming, every incorporated municipality with a population of 2,500 or more reported some boundary change during the decade. Ninety-five percent of the municipalities of that size in Nebraska, Arkansas, Idaho, Montana, Colorado, Utah and Oregon used annexation to grow.
On the other hand, no boundary changes were reported in New Hampshire or Rhode Island.
Many annexations occur because people outside city limits want city services, such as water, sewer, fire and police protection, Miller said.
In some cases, racial balance may also be a factor, with school enrollment and voting power taken into consideration.
As suburban areas gain political power in future years, annexation may become more difficult, Miller speculated. Suburbs, in many cases, are setting up their own governments and resist sharing their affluence and independence.
By region, Southern cities annexed the most people, 1.8 million, during the 1970s, followed by the West, 703,000; Midwest, 630,000; and Northeast, 9,000.