For years, SUVs and crossovers have been growing in popularity in the U.S.--entirely displacing the station wagon and reducing the population of minivans in family garages.

And now they've reached a significant milestone.

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This year, sales of crossover utilities and more traditional SUVs together have overtaken sedans in the U.S. market, according to data from IHS Automotive.

Sales of these vehicles accounted for 36.5 percent of U.S. new-vehicle registrations this year through May, against 35.4 percent for sedans.

Sedans have been on top for decades, and led the combined SUV and crossover segment 36.6 percent to 33.9 percent last year, according to the data.

2014 Toyota Highlander Hybrid, Palisades Interstate Park, New York, June 2014

2014 Toyota Highlander Hybrid, Palisades Interstate Park, New York, June 2014

While sedans remain popular, consumer interest in utility vehicles has steadily increased as well over the past few years.

The growth is largely due to the proliferation of crossovers, which are more car-like than traditional body-on-frame sport utility vehicles.

That means crossovers can offer buyers the space, high driving position, and all-wheel drive capability of an SUV, while still driving more like cars and offering better fuel economy.

So while crossovers are eating into sedan sales, they're actually pushing aside older-style SUVs. Only a few of those models are still offered by carmakers--mostly in the largest sizes--but the number of crossovers is multiplying.

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Even if the balance of sales tends to favor the more fuel-efficient crossovers, this trend may still pose a challenge for carmakers as they try to meet stricter emissions standards.

U.S. Corporate Average Fuel Economy (CAFE) standards require manufacturers to achieve a fleet average of 54.5 mpg by 2025. That's the equivalent of about 42 mpg on the window sticker.

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