The Census Bureau was established as a permanent agency in 1902, as industrialization and urbanization were bringing about rapid changes in American society. The years following the establishment of a permanent Census Bureau saw the first attempts at devising statistical geography for tabulating statistics for large cities and their environs. These efforts faced several challenges owing to the variation in settlement patterns, political organization, and rates of growth across the United States. The 1910 census proved to be a watershed, as the Census Bureau offered a definition of urban places, established the first census tract boundaries for tabulating data within cities, and introduced the first standardized metropolitan area definition. It was not until the middle of the twentieth century, however, the Census Bureau in association with other statistical agencies had established a flexible standard metropolitan definition and a more consistent means of tabulating urban data. Since 1950, the rules for determining the cores and extent of metropolitan areas have been largely regarded as comparable. In the decades that followed, however, a number of rule changes were put into place that accounted for metropolitan complexity in differing ways, and these have been the cause of some confusion. Changes put into effect with the 2000 census represent a consensus of sorts for how to handle these issues.