an example of a "reasonable restriction." Once New York had passed its law, other cities followed, although proposed zoning measures did meet stiff resistance in some places, often because of the inclusion of overly restrictive height limits, and sometimes because the entire concept of zoning was seen as undemocratic and bordering on socialism. Eventually, a model law, the Standard State Zoning Enabling Act of 1922 was drawn up for the guidance of cities wishing to enact zoning regulations, which are now part of virtually every American city. Central business district During the late 19th and early 20th centuries, the downtown area was the business district of the American city, but beginning around the 1920s and 1930s, as cities continued to grow in size and population, rival business districts began to appear outside of downtown in outlying districts. This was the time when the term "central business district" began to appear as more-or-less synonymous with the downtown area. The phrase acknowledged the existence of other business districts in the city, but allocated to downtown the primacy of being "central", not only geographically, in many cities, but also in importance. And in many cases, the downtown area or central business district, itself began to grow, such as in Manhattan where the business district lower Manhattan and the newer one in midtown began to grow towards each other, or in Chicago, where downtown expanded from the Loop across the Chicago River to Michigan Avenue. In fact, the instability of downtown was a cause for concern for business and real estate interests, as the business district refused to stay where it had been, and shifted its location in response to numerous factors, although it generally stayed fairly compact – in the early 1930s even the largest took up less than 2% of the city's space, and most were significantly smaller – and remained the primary business district of the city. Real estate interests were particularly concerned about the tendency of downtown to move because the downtown area had by far the highest land values in each city. One commentator said that if Chicago's land values were shown as height on a relief map, the Loop would be equivalent to the peaks of the Himalayas compared to the rest of the city. In 1926, Chicago's central business district, which took up less than 1% of the city, had 20% of the city's land value. The