Susan Crawford is a columnist for Backchannel and a professor at Harvard Law School. She is also the author of The Responsive City and Captive Audience. Sign up to get Backchannel's weekly newsletter.

Imagine that you are Jeff Bezos. For four hours two weeks ago, you were the richest person in the world. And though Wall Street knocked you down a notch, pretty much everyone thinks it’s inevitable that you’re going to be number one again. You’re starting to be aware of the smell of the tar pits and you’re casting about for a way to put all that loot to some good. You're eying the Gates-Buffet Giving Pledge and thinking that if you donate half your fortune it should make a difference. You're comfortable with making older but meaningful institutions great again.

So far, you’ve concentrated on things that might benefit our distant successors—space travel, cancer treatments, AI, and a clock that will keep running for 10,000 years. But you want to do something more immediate. You say you want your philanthropic activity “to be helping people in the here and now—short term—at the intersection of urgent need and lasting impact.” You are open to suggestions--so much so that you even recently tweeted a “request for ideas.”

Though you don’t mention it, I suspect you’re thinking of stepping into an area that traditionally government might have addressed—but now, in an era in which the wealthy are doing better and better, benefits seem to go toward the top while the “urgent needs” of just plain people are left to the grace of a harsh marketplace. Like it or not, citizens are increasingly dependent on the kindness of strangers with billions of dollars,

I have a suggestion for you, Jeff Bezos. How would you like to become the Andrew Carnegie of our time?

Yes, I am talking about libraries. Those places where books sit on shelves, not delivered by FedEx. And so much more. Carnegie made them the center of his philanthropy, and almost became synonymous with them. More importantly, he changed countless lives with his investments in libraries. I have heard that you’re looking for big ideas, and this is one.

Today, local libraries are thought of as slightly retro public institutions. For some reason, major donors don't get excited about them. OK, there are some notable exceptions to this rule—in my adopted city of New York, for instance, Stephen Schwarzman has his name engraved on the main branch building of the public library; in Kansas City, the Kemper family has donated millions to the downtown branch and a Kemper scion, R. Crosby Kemper III, has been the executive director of the library for more than 12 years.

But the real impact—the one that changes lives and transforms communities—has yet to be made. It turns out that libraries are the very model of the more-than-shovel-ready, here-and-now, urgent-need-and-lasting-impact places that you as a tech philanthropist claim to be interested in supporting in a big way. And libraries’ needs are dire.

You, Mr. Bezos, may not have been inside a library in a while. Things have changed. Today, libraries are serving as essential civic places. Trusted by every part of American society, they're the only noncommercial places other than city squares where people meet across genders and ages. They provide all kinds of services and programming—just visit the glorious Madison, WI Central Library, where a first-rate makerspace is under the same LEED-certified roof as local service agencies helping people sign up for health care and food assistance.