Sitting unnoticed on the streets of Wilmington, Delaware is a bland, two-story office building called the Corporation Trust Center, a name that is quite unfitting considering that what happens behind its glass doors are some of the very least trustworthy corporate activities.

1209 North Orange Street is the legal address of a whopping 285,000 American businesses as of 2012, making the little Corporation Trust Center the largest corporate facility in the world by a number of firms. As the registered home of Google, Apple, Walmart, American Airlines, J.P. Morgan Chase, and Coca-Cola, the center is home to more businesses than there are people in Wilmington.

What draws companies to the Corporation Trust Center is not its drab, yellow brick exterior, but rather the Delaware General Corporation Law (DGCL), often referred to as the single most important corporate jurisdiction since the beginning of the 20th century. The DGCL allows businesses based in other states (including, ahem, yours truly) to file their taxes in Delaware, whose unusually low corporate tax rate saves major corporations billions in taxes.

The DGCL is so lucrative for big business that over 300 of the Fortune 500 are incorporated in Delaware. It’s so corporate friendly, in fact, that every year, 15% of all public corporations in the United States use the exact same building as their tax haven. These hundreds of thousands of tax-avoiding businesses include firms under the names of the two 2016 presidential candidates: For all their many differences, Hillary Clinton and Donald Trump both have companies registered at the same Orange Street address.