While establishment of the agricultural preserve and the land trust has slowed residential development in much of the county, residential growth within the incorporated cities has continued at a moderate pace. Several substantial homes have been built on the hills surrounding the valley in areas not covered by the preserve or the land trust. A large portion of the land south of the City of Napa remained undeveloped for many decades until the 1980s. Several wine bottling facilities and wine storage warehouses now stand on what was once vacant land. A number of light industries have also sprung up in this region as new business parks have been built. The growth of American Canyon, Napa County's southernmost and newest city, incorporated in 1992, has prompted the establishment of several new retail outlets in the southern end of the county in recent years. American Canyon has also established a green belt preserve of over on the western and eastern sides of the city.