Downtown Minneapolis evolved from a collection of modest frame buildings on the banks of the Mississippi River to the high-rise center of a modern American metropolis. With a burgeoning milling industry powering the local economy, the early frame structures soon gave way to substantial brick and masonry buildings, lining the streets of a bustling 19th-century commercial district. Downtown continued to prosper during the early years of the 20th century, aided by advances in transportation and communications. The heart of the city held its own during the Great Depression and World War II, but the postwar era brought new challenges as a suburban boom threatened the city's economic foundation. Enterprising local leaders responded with innovative developments to meet these challenges, and a reinvigorated downtown took on a new role as the site of a dynamic new residential community, now home to nearly 40,000 city residents.