The U.S. land mass was 3,554,608 square miles in 1940; in 1990 it had declined to 3,536,278, The New York Times reported Saturday.
However, geographers said most of the difference is a result of improved satellite imagery and other mapping technology that makes it easier to distinguish land from water.
If America's land mass is shrinking, its territorial waters are growing. Since 2000, the nation's official measurement of territorial waters rose to 264,837 square miles, from 256,645.
The report also said the Borough of Queens in New York shrank by 1 square mile since 2000, possibly as a result of erosion and rising sea levels in the Jamaica Bay unit of the Gateway National Recreation Area.
"For area measurement purposes, hydrologic features identified as intermittent water, glacier, or swamp are reported as land area," the Census Bureau said. "Identification of land and inland, coastal, territorial, and Great Lakes waters is for data presentation purposes only and does not necessarily reflect their legal definitions."