Every four years, the American Society of Civil Engineers issues a report card on the condition of the nation's infrastructure. In 2013, the last year a report was released, the country received a sad D+ – something that then-candidate Donald Trump highlighted during his presidential campaign. (See also: Build Your Portfolio With Infrastructure Investments.)

As president, Trump has promised up to $1 trillion in new spending to spruce up the nation's crumbling infrastructure, a prospect that should encourage investors who seek exposure to this niche. (See also: How Big Investors Will Profit From Trump's Infrastructure Bonanza.)

It is important to note that infrastructure is an extremely broad category, encompassing transportation, communications, water and electricity – representing hundreds, if not thousands, of equities. Selection is essential to success, since not all "infrastructure" stocks will take off under the proposed spending. (See also: 4 Reasons You Should Worry about the U.S. Economy.)

That being said, well-diversified companies positioned to handle major infrastructure projects should do well over the medium to long term, especially if the administration follows through with its spending commitment. Here's a look at four of the most promising infrastructure stocks. All figures are accurate as of August 4, 2017.

AECOM (ACM)

AECOM's business is designing, financing, building and operating infrastructure assets for federal and state governments and businesses. With a market cap of just under $5 billion and fiscal 2016 annual revenue of $17.47 billion, the company is well positioned to handle a large influx of new government projects.

AECOM recently merged with rival URS to enhance its focus on the energy and transportation sectors, areas that are sure to see new spending under the Trump administration if the president can pass his infrastructure package. In fact, AECOM stock surged sharply on Trump's victory, rising from $27.61 on Nov. 8, 2016, to $37.54 a week later, reaching a high of over $40 in December 2016. As of August 4, 2017, the stock was trading at around $31, equating to a decline of roughly 10% over the past year. The stock has a median 12-month price target of $38, suggesting 22% upside potential, and it earns a consensus rating of Outperform. (See also: AECOM to Buy Shimmick, Make Most of Infrastructure Spend.)

Vulcan Materials Company (VMC)

"Construction aggregate" sounds like a boring business, but these little bits of gravel, limestone and sand form the foundation of all sorts of building projects, including high-priority infrastructure items such as bridges, roads and industrial plants. Vulcan is the largest producer of these construction products, and it estimates that 75% of the population growth in the coming years will take place in states currently served by the company.

Vulcan has a market cap of $16 billion and generated annual revenue of $3.59 billion in 2016, which equates to a revenue growth rate of nearly 9% year over year. As of August 4, the stock was trading at $122, a one-year increase of about 3.5%. Its median price target is $145 (implying 19% upside potential), and the consensus rating is Outperform. (See also: Vulcan Materials' Inorganic Growth in Full Swing.)

Martin Marietta Materials, Inc. (MLM)

Martin Marietta is a leading manufacturer of cement, asphalt and other building materials, with a strong presence in states such as North Carolina, Texas, Colorado and Georgia that have booming construction economies. The company recently kicked off a massive project in Texas known as the Medina Rock & Rail, strengthening its foothold in the lucrative Texas market. Last year proved to be a record year in terms of the company's revenue, which hit nearly $3.9 billion.

Martin Marietta is based in Raleigh, North Carolina, and it has a market cap of $13.5 billion. Net income was up last year by 47% to $421 million, and earnings per share rose 31% to $6.63. The stock currently trades at about $214, up over 8% over the past 12 months. The average 12-month price target of $250 suggests upside potential of over 15%. (See also: Martin Marietta to Buy Bluegrass, Boost Aggregates Business.)

Quanta Services, Inc. (PWR)

Quanta is a specialty contractor providing infrastructure services primarily to the oil and gas and electrical power industries, all of which stand to benefit under Trump's infrastructure spending plans. Quanta is also a prime provider of oil and gas pipelines and renewable energy infrastructure, including onshore and inland hydroelectric projects.

Quanta has a market cap of $5.5 billion and posted annual revenue of $7.65 billion in 2016, on par with the previous year's revenue of $7.57 billion. As of August 4, the stock was trading at $36.50, up almost 55% over the previous 12 months. Its 12-month price target of $43 leaves room for 17% growth. (See also: Quanta Services Q1 Earnings Miss, Revenue Up Y/Y.)

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