Image: Blue-chip stocks © Sandra Baker, Getty Images

You may not recognize their names, but a host of midsize companies are poised to be the brand names of the future -- at least as far as investors are concerned.

They're companies such as CH Robinson Worldwide (CHRW), which has become the (PCLN) of the industrial-transportation world while recording 17% annual earnings growth over the past decade; Generac (GNRC), which is seeing demand explode for its home generators; and Catamaran (CTRX), which helps Americans cut through the clutter of drug-benefits management.

Not surprisingly, shares of these fast-growing, high-quality companies don't come cheap. But when you buy tomorrow's blue chips -- companies that stand a good chance of graduating to gargantuan status and that are likely to thrive in the toughest economic environments -- you have to be willing to pay up a bit. This kind of stock can serve as a cornerstone of your portfolio for decades to come. "Whenever I find a company that is really durable and able to grow 10% to 15% a year in any economy, I am willing to give it a little more leash," says Joe Milano, manager of the T. Rowe Price New America Growth Fund (PRWAX).

Below we identify six fast-growing midsize companies (none of them household names) that are likely to deliver solid returns to shareholders for years to come:

Aircraft leaser

Air Lease (AL) buys and leases out commercial aircraft. Launched about three years ago as the economy was just coming out of recession, Air Lease is both the youngest and smallest company on this list, with a market value of $2.2 billion. But it's not likely to stay small for long. The Los Angeles company has amassed a fleet of 142 planes, which it has leased to 66 airlines around the world. In the process, revenues and profits have soared. During the first nine months of 2012, Air Lease's revenues doubled from the same period in 2011, and earnings more than tripled.

And Air Lease isn't close to cooling its jets. By the end of 2012, it had secured commitments to lease all 70 of the aircraft it is slated to receive between now and the end of 2014, as well as a number of the planes that will be delivered in 2015 and 2016. Analysts expect Air Lease -- which is headed by Steven Udvar-Házy and John Plueger, the former top dogs at International Lease Finance -- to generate annual earnings gains of 43% over the next three to five years.

Maxim Group analyst Ray Neidl says that although Air Lease's price-earnings ratio is higher than that of many of its rivals, the stock is worth it. Not only have the company's execs proved adept at buying and leasing aircraft at good prices, the business is booming. Aging aircraft fleets here and abroad require updating. Even if global economic growth remains subpar, airlines should see the benefit of leasing from Air Lease's more fuel-efficient fleet. Neidl sees the stock climbing to $28 within a year.

Drug-benefits manager

Catamarans are sleek, double-hulled boats adept at cutting through water. Catamaran makes its mark by slicing through health care paperwork to manage pharmacy benefits for some 25 million Americans. What gives the Lisle, Ill., company an edge is that it started as an information-technology provider, selling management systems to other drug-benefits managers. That means its software is state-of-the-art, says Brooks O'Neil, an analyst with Dougherty & Co.

Better technology means better monitoring, which translates into more-effective health care at a more affordable price. The old system, in which people handed pharmacists written prescriptions, often resulted in patients receiving a shopping list of drugs that sometimes reacted poorly with one another and created new medical problems. Catamaran's software spots potential drug conflicts. And at a time when a growing number of people suffer from chronic ailments such as diabetes and high blood pressure, Catamaran's systems can even alert doctors when it appears that a patient isn't keeping up with his or her medications. The company's software flags files when maintenance drugs aren't renewed on schedule.

Catamaran's growth has been stunning. The company rang up sales of $93 million in 2007. In the first nine months of 2012, revenues were $6.6 billion, and O'Neil thinks the figure will reach $15 billion in 2013 and grow at an annual rate of 30% to 40% for some time thereafter. That's partly because as the population ages, the whole pharmacy-management industry is growing. But it's also because Catamaran is nabbing an increasing share of the market, a trend that O'Neil is convinced will continue. With a market value of $10.3 billion, Catamaran edges C.H. Robinson for largest company on our list.

Blackout beneficiary

There's nothing like a rash of storm-related power outages to get people thinking about springing for a backup generator. And that spells opportunity for Generac. A maker of both portable and standby generators, as well as power washers and portable floodlights, Generac has generated annual earnings growth of 68% over the past three years.

The Waukesha, Wis., company controls 70% of the market for standby home generators. These devices -- Generac's cornerstone product -- are permanent fixtures that are attached to a gas line and connected to a home's electrical system. Unlike the typical portable generator, which needs to be started up and connected to the house with extension cords, Generac's standby system flips to generator power virtually automatically. Although Generac's standbys cost more than portable generators, the company has found that about half of those who buy movable systems eventually trade up to a standby model. Because some 12% of Americans have portable systems and just 2.5% have standby generators, Generac could easily double its business. The company is also expanding overseas and boosting its power-washer and portable-lighting businesses. Jeff Hammond, an analyst with KeyBanc Capital Markets, thinks that combination will result in double-digit profit growth for many years to come. He sees the stock at $41 within 12 months.

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