A proposal to turn an abandoned parking lot in a small Chester County borough into a seven-story development is the latest in a string of residential-retail buildings popping up across the county.

After decades of outward expansion in the suburbs, places such as Downingtown have recognized that "the last thing [left] to do would be to go up," said Steve Plaugher, manager of the Downingtown Main Street Association.

The proposal is still in an early stage and has yet to be approved by the borough, but developer Andrew Hicks of Tripoint Properties said he would hope to make the building into a landmark.

It would be a big step for the borough, which does not have any buildings as tall as the proposed condo-retail combo.

"This type of development is something that isn't typically seen in a suburban borough. This building looks like something you'd see in University City," said Mayor Josh Maxwell.

Yet such projects are increasingly visible in the suburbs - often in trendier towns hoping to attract young people and well-to-do residents with homegrown breweries, urban-style restaurateurs, and expanding arts scenes.

Eastside Flats, a retail-residential development in Malvern built in 2013, helped lead the mixed-use trend in Chester County.

"That model is being played out in most of the boroughs in the downtown areas that we can identify," said MaryFrances McGarrity, director of business development at the Chester County Economic Development Council.

Chester County is the fastest-growing county in the region, according to census data through July 2014, largely because of development along the Route 202 corridor. The county's population increased by about 18 percent between 2000 and 2014.

In Devon, 20 miles east of Downingtown, a proposed six-acre development including four stories of luxury apartments and anchored by Urban Outfitters' Anthropologie and Terrain stores is going through the Easttown Township approval process.

In Downingtown, Plaugher said, he hoped the development would put "positive pressure" on neighboring businesses to spruce up their storefronts to "keep pace with the modern development."

The seven-story Union Place would include condominiums with stores below and a parking garage for both residential and public parking.

Borough Councilwoman Ann Feldman said the project would not help preserve Downingtown's character as a "sleepy mill town."