Have you ever wondered what the largest company is in your city? I did. I'm in Columbus, Ohio, and I was sure that Nationwide Insurance was the largest company (by revenue) here. I was wrong. It turns out there's an entire JP Morgan Chase entity based right here in my hometown. So that got me wondering about other big cities. And an easy search shows that the largest cities in the world rarely are home to the largest companies.

According to U.S. Census statistics from July 1, 2006, the 10 most populated cities in the United States are:

1. New York City

2. Los Angeles

3. Chicago

4. Houston

5. Phoenix

6. Philadelphia

7. San Antonio

8. San Diego

9. Dallas

10. San Jose

See if you can guess the biggest company in all these cites. Read on to find out if you're right.

New York City

When you think of NYC, you think of money, so this is probably an easy one to guess. Despite a disastrous couple of years, Citigroup is still No. 1 in NYC. One of the largest financial services firms on the planet, Citigroup has offices all over the world.

Los Angeles

When you think L.A., you think Hollywood studios, right? Wrong. In fact, it's unlikely you'll ever see a celebrity wandering the halls of LA's largest company. Northrop Grumman is the world's No. 1 shipbuilder and a top defense supplier. The company made news in early 2008 after being awarded a hefty contract to build Air Force refueling tankers. Northrop Grumman's partnership with Netherlands-based Airbus sparked a ?Buy American? outcry from its archrival Boeing Corp.

Chicago

Speaking of Boeing, would it surprise you to know that the aerospace company (of Seattle-area fame) is actually the largest company based in Chicago? With more than $61.5 billion in sales in 2007, the profits keep flying in the windy city.

Houston

It's Texas, so it must be oil. But it's not ExxonMobil or Chevron that dominates the Houston market. Its ConocoPhillips, formed by the merger in 2002 of Conoco and Phillips Petroleum. The company owns Marathon Oil Corp. but did you know ConocoPhillips also owns Continental Airlines and trash giant Waste Management?

Phoenix

Spring training, sun and semiconductors? That's right. The biggest company in Phoenix is Avnet, Inc., one of the world's largest distributors of semiconductors, electromechanical components and other technology products. Another Phoenix tidbit: Petsmart, the nation's largest pet services store (and a personal favorite of my pooch) is No. 4 in Phoenix.

Philadelphia

When Ben Franklin flew that kite in the 18th century and jump-started America's insatiable need for energy, he may never have dreamed that in the 21st century, his City of Brotherly Love would be home to one of the largest petroleum refining companies in the world. Formed by the merger of many other companies, Sunoco has been around in one form or another since 1905.

San Antonio

It seems like sun and energy companies go hand in hand. Topping all other companies in San Antonio is Valero Energy. Named after the Alamo (the Mission San Antonio de Valero), the company is the largest independent oil refiner in the U.S.

San Diego

And in keeping with the energy theme, San Diego-based Sempra Energy serves the largest customer base of any energy utility in the United States. Maybe they've figured a way to turn sun, surf and sailors into renewable energy.

Dallas

Dallas means big oil and big hair, but neither ExxonMobile nor Nieman-Marcus is tops in Dallas. (Exxon's based in nearby Irving; Nieman's is only Dallas? 13th largest company.) But Dallas? largest company depends on who you ask and when. Homebuilder Centex Corp. and tech maker Texas Instruments are so close in earnings that the No. 1 ranking is constantly changing.

San Jose

The only question when trying to guess the biggest employer in San Jose is which tech company is on top. That'd be Cisco Systems, the ubiquitous maker of network routers, switches and other computer peripherals.