The history of urban America is in reality, the history of zoning in urban planning. For a long time, zoning has affected real estate development, labor distribution and housing arrangements in the United States. However, since the United States officially entered the "zoning system" era in 1916, urban planners have been arguing if urban construction should be carried out according to top-down planning, or respect the laws of organic growth. Today, the weak performance of American cities such as New York and San Francisco under the zoning system against the COVID-19 pandemic has forced people to re-examine the advantages and disadvantages of zoning.

As the most commonly implemented urban planning method in American cities, "zoning" has been used in megacities like New York and San Francisco for over a century. The earliest modern zoning plan in the United States was the 1916 Zoning Resolution promulgated by New York City in 1916. The original intention of the resolution was to control the disorderly growth of skyscrapers and to ensure that the tenants' sunlight would not be blocked out. According to the resolution, the five administrative districts of New York would be divided into residential, commercial, and mixed districts, each with a restricted amount of land to be used. Due to the zoning system's control of buildings and that its functions ensure the appreciation of land and properties, as well as stabilizing government taxation and promoting urban economic development, more and more cities in the United States are starting to imitate New York's "zoning system".

However, there are two sides to every coin. Rigorous zoning has led to separation and isolation in its use of land, which intensified the division of the American society. Due to the expansion of the city, large-scale zoning governance has led to the lack of public service facilities and a waste of infrastructure and land resources. Especially with the popularity of cars, urban zoning has widened the distance between residential areas and the city center, thus creating large areas of low-density, low-volume residential areas that lack pedestrian streets and are far from commercial and shopping centers. At the same time, due to the consideration of maintaining and increasing the value of real estate in an area, the local government has used zoning regulations to limit the area, unit type, floor area ratio and other factors of the property, artificially highlighting the social class in a given space, which undoubtedly increased social conflicts between different classes and brought about hidden dangers to public order.

With the emergence of the COVID-19 pandemic, damage caused by the "zoning system" to big cities have only been amplified. This has also intensified the heated discussion regarding whether urban planning should be unified or given freedom to grow. Typical of the "zoning system," New York and San Francisco have been slow to react during the pandemic, which is mainly reflected in the zoning regulations that restrict urban mobility and industrial flexibility.

A decline in urban mobility is the first problem that cities with a "zoning system" faces during the pandemic. As zoning increases the distance between work and residence, people have to rely on either public transportation or private cars in order to commute. However, in the post-pandemic period where COVID-19 has not been completely eliminated, most people will not choose public transport as it would be overly crowded. As a result, more cars would start appearing on the road, causing problems such as traffic congestions and insufficient parking spaces. If this goes on, the commuting time of the people would increase much more than what it previously was before the pandemic, resulting in greatly weakened urban mobility. More and more people would have to abandon their original jobs and find jobs closer to their residences where job opportunities are much scarcer. This poses a serious ripple effect, where the housing and rental market will be affected. Due to the decline in urban mobility, companies have to follow the example of Twitter and Facebook by allowing their staff to work from home in order to ensure efficiency. However, this has directly led to the downturn in housing and rental housing markets in many major cities such as New York, San Francisco, and Seattle. According to data research by real estate company Douglas Elliman, the vacancy rate of rental housing in Manhattan, New York, reached a record-breaking 5.75% in September 2019. Data from the New York Small Landlord Association also proves that the vacancy rate in September 2019 was 12%, an increase of 9 percentage points from February of the same year. Homes listed for sale in San Francisco rose 96% year-on-year, and rents in September fell 31% year-on-year.

Lack of industrial flexibility would be the second problem that cities that implement the "zoning system" will face. Take San Francisco as an example. The zoning of the city is almost paranoidly strict, where there are complex and detailed requirements in zoning regulations. According to a recent report from the Mercatus Center of George Mason University, some areas in San Francisco where schools are allowed to open have prohibited the opening of vocational schools; there are also areas where the sale of new cars is allowed and yet the sale of used cars are prohibited, restaurant areas are prohibited from catering services and so on. Not only that, San Francisco's complex zoning system also restricts outdoor dining, and even applications to reopen would require at least one month's review and approval. This has directly led to the fact that a large number of shops have had to close down during the pandemic as they were unable to utilize outdoor space to start business. Some businesses that want to change the nature of the industry have no room to operate. They can only watch on as they slowly lose funds and had to shut down their businesses. It took a full 6 years for an abandoned mall in the San Francisco Bay Area to be allowed to transform into housing, which shows that the flexibility of the industry under the "zoning system" has been greatly lost.

Comparatively, as one of the few major cities in the United States that rejected the "zoning system", Houston has demonstrated amazing economic flexibility and resilience in this pandemic. Take the hotel industry as an example. Due to the pandemic, it has experienced plenty of difficulties. In order to reverse this situation, most hotels in Houston have undergone a hybrid functional transformation and introduced other operating methods. As Houston was not designed with a "zoning system", this change was not met with much resistance. Therefore, the local hotel industry can quickly transform and restore its vitality. In fact, long before the pandemic, Houston's free and organic urban planning model had already revealed its unique advantages. Although the population is only one-third of New York, Houston's new home completion rate in 2019 has caught up with New York. Moreover, Houston, which has no zoning restrictions, does not burden residents with traffic and housing problems like other large cities. Although Houston is often criticized for its never-ending rural expansion, people who grew up in Houston hardly leave or move to other big cities because they prefer the local multi-purpose community where integration of living, working, and entertainment lifestyle are its main advantages.

Decades after its reform and opening-up, China's urbanization has accelerated rapidly. As the theoretical system of Chinese urban research is basically imported from abroad, led by Western-educated urban planners and architects, the concepts and ideas of zoning planning are naturally also learnt and imitated by such planners. In the context of China, zoning planning is a part of the territorial and spatial planning system, it is the concretization of the municipal-level territorial and spatial master plan. The zoning plan needs to convey the objectives, indicators and tasks determined by the overall plan to the upper level, and to provide guidance for lower-level planning. Although China's zoning plan is different from that of the United States, in the post-pandemic period people have once again disputed zoning planning in the United States, which serves as a reminder to the Chinese urban planners to rethink about its applicability, to pay attention to the constraints brought about by strict functional zoning planning to urban flexibility, and to reflect on locating a balance between zoning planning and the organic growth of the city.