Mid-cap stocks have the best odds of scaling into $100 billion corporations thanks to their tested business models and large addressable markets. But the many opportunities in front of them attract significant competition, spanning from industry behemoths with seemingly infinite resources to small, nimble players with chips on their shoulders.

Luckily for you, our mission at StockStory is to help you make money and avoid losses by sorting the winners from the losers. That said, here are two mid-cap stocks with long growth runways and one best left ignored.

Market Cap: $9.58 billion

Headquartered in Irving, TX, Builders FirstSource (NYSE:BLDR) is a construction materials manufacturer that offers a variety of lumber and lumber-related building products.

Why Are We Out on BLDR?

Annual sales declines of 5.7% for the past two years show its products and services struggled to connect with the market during this cycle

Earnings per share decreased by more than its revenue over the last two years, showing each sale was less profitable

Eroding returns on capital suggest its historical profit centers are aging

Builders FirstSource is trading at $87.14 per share, or 15.3x forward P/E. Check out our free in-depth research report to learn more about why BLDR doesn’t pass our bar.

Market Cap: $11.21 billion

Built as an alternative to "walled garden" advertising ecosystems, The Trade Desk (NASDAQ:TTD) provides a cloud-based platform that helps advertisers and agencies plan, manage, and optimize digital advertising campaigns across multiple channels and devices.

Why Is TTD a Top Pick?

Annual revenue growth of 22% over the last two years was superb and indicates its market share is rising

Software platform has product-market fit given the rapid recovery of its customer acquisition costs

Highly efficient business model is illustrated by its impressive 20.3% operating margin, and it turbocharged its profits by achieving some fixed cost leverage

At $23.53 per share, The Trade Desk trades at 3.7x forward price-to-sales. Is now a good time to buy? Find out in our full research report, it’s free.

Market Cap: $23.24 billion

Founded by a mother seeking treatment for her daughter's pulmonary arterial hypertension, United Therapeutics (NASDAQ:UTHR) develops and commercializes medications for chronic lung diseases and other life-threatening conditions, with a focus on pulmonary hypertension treatments.

Why Will UTHR Outperform?

Annual revenue growth of 16.9% over the past two years was outstanding, reflecting market share gains this cycle

UTHR is a free cash flow machine with the flexibility to invest in growth initiatives or return capital to shareholders, and its rising cash conversion increases its margin of safety

Improving returns on capital reflect management’s ability to monetize investments

United Therapeutics’s stock price of $530.20 implies a valuation ratio of 19.5x forward P/E. Is now the right time to buy? See for yourself in our in-depth research report, it’s free.

ALSO WORTH WATCHING: Top 5 Momentum Stocks. The best time to own a great stock is when the market is finally noticing it. These aren't just high-quality businesses. Something is happening with them right now. Elite fundamentals meeting near-term momentum — both boxes checked at the same time.

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Stocks that made our list in 2020 include now familiar names such as Nvidia (+1,326% between June 2020 and June 2025) as well as under-the-radar businesses like the once-small-cap company Exlservice (+354% five-year return). Find your next big winner with StockStory today.