Until recently, few have questioned the notion that the separation of uses in land use zoning is inherently correct. Many observers of the city are now suggesting that zoning, as it has been practiced in this country over the last 80 years, has created cities that are fractured and function poorly. Others propose that zoning should be reconsidered as a remedy for urban dysfunction. They suggest that the whole notion of zoning be rethought. The purpose of this study is to uncover some of the underlying rationales and methodologies that set the model for zoning. This study examines the rationales behind the classification and location of land use zones in a fast-growing area of Portland, Oregon, for its first zoning ordinance through history, culture, and geography. Between 1919 and 1924, two ordinances were prepared using two very different methodologies. The first of these was designed by nationally known consultant, Charles H. Cheney, using the latest scientific methods. After its rejection in the polls, a second ordinance was developed by a prominent group of realtors in conjunction with the city planning commission using more intuitive methods. This “realtors’ code” (MacColl 1979) was approved by the Portland electorate in 1924. Some fifty years later, the Portland planning commission would identify zoning as having played a significant role in the deterioration of the Buckman neighborhood in the study area. The comparison of the rationales and methods behind the locations of zone boundaries in both ordinances against the locations of actual uses in the study area, reveals the powerful influences of social Darwinism, laissez-faire attitudes, and newly developing social science methods on the association of zoning with the separation of uses and the land use patterns that were created.