What gave city landowners the incentive to grow upward rather than outward?

City landowners were incentivized to grow upward rather than outward primarily due to the high cost and limited availability of urban land. As cities became more densely populated, the value of land increased, making vertical construction, such as high-rise buildings, a more profitable investment. Additionally, zoning regulations often encouraged or mandated higher-density developments, further promoting upward growth to maximize space and accommodate more residents or businesses within a smaller footprint. This shift also allowed for better utilization of infrastructure and resources in urban areas.