The population growth in southwestern Butler County is leaving some of the area’s boroughs feeling squeezed as a result.

For example, Zelienople is bordered by Jackson Township to its north, southeast and south and the borough of Harmony to the northeast. The western border of the borough is the Beaver County line.

Tom Oliverio, who has been the borough’s mayor since 1990, said of Zelienople: “It’s like a croissant. We’ve got Jackson Township to the north, east and south. The rest is Beaver County.”

There’s no ability to expand or annex land, Oliverio said, leaving the borough to embrace a future very different from that of the expanding townships in the same southwestern corner of Butler County as Zelienople.

Oliverio said there’s a new subdivision on Route 68 on the west side of Zelienople, but he figures that’s about the limits of growth for the borough.

Still, the borough has to contend with the effects of the population growth in Jackson Township.

According to U.S. Census Bureau numbers, the population of Jackson Township grew from 3,657 people in 2010 to 4,883 in 2020.

New sewer lines from the township are connecting with Zelienople’s 100-year-old sewer system, he said. “They are getting mainly new lines coming to the old.”

Oliverio said to head off future problems with the sewer system, he hopes that a committee made up of representatives of Zelienople, Harmony and Jackson and Lancaster townships can be set up to study the situation “in the next few years.”

It’s a case where the sooner it happens, the better, he said, because population growth for the nearby township is expected to increase.

Jackson Township’s population is projected to grow significantly, potentially reaching 25,000 to 30,000 residents within 20 to 30 years, according to Butler County and Jackson Township officials.

The growing population outside the borough is also reflected in the changing face of downtown Zelienople.

“There has been a lot of new businesses. In the last four or five years, I’ve been to 30 ribbon-cutting ceremonies, seven or eight so far this year,” he said.

He noted the new owners are younger, in their 30s and 40s, and coming from outside the borough. Many are women.

“There are plenty of dress shops, jewelry stores. Zelienople is not designed for men anymore,” Oliverio said.

Oliverio estimated that 85% of the business owners in Zelienople come from out of town. They come from Butler, Elwood City and sometimes Cranberry Township, he said.

“You can’t buy a pair of shoes anymore. It’s white collar versus blue collar. Blue-collar people still live in Zelienople, but the white collars are on Main Street,” he said.

In the nearby borough of Evans City, Council President Cheri Deener-Kohan said the growth of the surrounding townships has definitely affected her borough.

According to the United States Census Bureau, Evans City has a total of area of 0.81 square miles of land.

Evans City is bordered on the north, west and south by Jackson Township and to the north, east and south by Forward Township

Route 68 passes through the borough, leading northeast 12 miles to Butler and northwest 5 miles to Zelienople.

“It’s all transit. It just goes right through town,” Deener-Kohan said.

As of the 2020 census, there were 2,061 residents in the 0.8-square-mile borough. Deener-Kohan doesn’t see the borough’s population growing significantly in the future.

“There’s no work in town. There’s one plant,” she said, although she noted younger people are moving into town because of Evans City’s affordable housing.

Deener-Kohan said possible future development may entice some of the traffic on Route 68 to stop in Evans City.

“We have a lot of open store fronts,” she said. “One person has bought a lot of the area and is working to revitalize it.”

She doesn’t see the surrounding population growth as having any effect on the borough’s budget.

“We’ve been used to it. There’s nothing new in the budgeting process. We’re raising taxes to keep up with the general budget,” she said.

The millage rate in Evans City is currently 24.750. The millage in Jackson Township is 10.250.

Mars also finds itself hemmed in because it is surrounded by a growing Adams Township. There’s very little room for Mars to expand beyond its present 0.5 square-mile border, said Mayor Gregg Hartung.

“We have possibly 22 acres on the west side of the borough that could be developed,” he said. “It’s privately owned property, it’s hilly terrain. It could be developed if someone had a lot of money.”

He noted there’s increased traffic because the borough is in the middle of all the developments. “There’s an increase in police and infrastructure because of all the buildup,” he said.

He said Mars is fortunate it doesn’t have to depend solely on property taxes to fund its operations.

“We have our own water system, one of the better water systems. We can sell that water, and it helps us stabilize the budget,” he said.

And, Hartung noted Mars is getting a break on street repairs because Peoples Gas is updating gas lines in the borough and the utility has to repair the streets when its done.

One item affected by growth, he said is the Mars library. It serves Mars, Valencia and Middlesex and Adams townships.

“We’re looking with three or four other municipalities to best see how the library can serve them either here or in one of the other municipalities. We would love to have the library stay here. Community and library members will make the final decision,” Hartung said.

He said Mars had joined with Adams Township, Seven Fields and Valencia boroughs and portions of Cranberry, Middlesex, Forward, Pine and Richland townships in the Breakneck Creek Sewer Authority.

“I think the challenge for Mars, Evans City, Saxonburg is that they are older than the developments around us,” he said.