The Bay Area, long the center of America’s tech industry, exemplifies this urban shift. This was once the paradigmatic suburban nerdistan based in the corporate campuses of Silicon Valley. But today San Francisco pulls in more venture capital than the Valley itself. And together more than half of the venture capital investment in the combined San Francisco and San Jose metro areas went to either center cities or walkable suburbs. The city of San Francisco – which attracted more than 50 percent of its metro areas venture capital – is the epicenter of this urban growth. The newly renovated headquarters of Yelp in downtown San Francisco, which Alexis Madrigal cataloged for the The Atlantic a few weeks ago, is one exemplar of this urban tech resurgence.

In San Francisco it's not just Yelp -- it's Salesforce, Twitter, Square, Pinterest, Zynga, and many more.