Pity Seattle--or don't. It depends what you think about Denver's rapid growth. Seattle has fallen behind Denver when it comes to the nation's largest cities in terms of population, as the Seattle Post-Intelligencer  writes of new Census Bureau estimates. Denver, with a population about 1,300 people shy of 600,000, is now the nation's 24th largest city and one of the fastest growing, too. Denver--sandwiched between Seattle and Milwaukee, at 23rd largest--is also 25th in terms of fastest-growing cities, according to the Denver Business Journal . Ranking slightly faster than Denver in terms of pace of growth were Thornton and Aurora, making the region an expanding metro area. New York is still the largest city in the nation, with 8.36 million people, and New Orleans is the fastest-growing.