At the end of the nineteenth century, the Inland Empire was a major center of agriculture, including citrus, dairy, and winemaking. Agriculture declined in the twentieth century. Since the 1970s a rapidly growing population came in search of affordable housing. This led to more residential, industrial, and commercial development. The area has a population of about four million.
- "Annual Estimates of the Population of Combined Statistical Areas: April 1, 2000 to July 1, 2010". 2006 Population Estimates. U.S. Census Bureau, Population Division. April 7, 2010. Archived from the original (CSV) on September 14, 2007. Retrieved December 2, 2007.