Seniors older than 65 years contribute to a progressively massive section of US society, close to 40.3 million in 2010, recorded the US Census Bureau while reporting on Wednesday.
In just a decade, the age group -- which numbered 35 million back in 2000 -- surged by 15.1 percent, even as the population as a whole increased by 9.7 percent.
In certain subgroups, the increases among seniors were huge: people from ages 85-94 increased in number by 29.9% (5.1 million compared to 3.9 million 10 years earlier) and people from 65-69 increased in number by 30.4% (12.4 million compared to 9.5 a decade ago).
But those from 75-79 actually decreased from 7.4 million to 7.3 million (-1.3 percent), reflecting a low birth rate in the Depression-era early 1930s.
Southern US states are home to far many older Americans: 14.9 million compared to just 7.8 million in the northeast.
Florida, a fabled sun-and-sand destination for US retirees, had the highest proportion of elderly, at 17.3 percent. Alaska sent seniors scrambling, with just 7.7 percent of the population over 65, the data showed.
The number of centenarians surged by 5.8 percent in 10 years, to 53,365 over 100 in 2010.