In 1967, as suburban growth hopscotched across the United States and vast tracts of farmland became townhouses and apartments, Baltimore County’s planners drew a line on the county map — and in the history books.

Two-thirds of the county — mostly the northern part, but with tufts on the west and east sides — would remain in conservation, with limited opportunities for growth. The remaining third — which included Towson, Pikesville, Catonsville, and most of the well-known communities — would have public water and sewer as well as managed growth.

The line held, even as the county’s population tripled. For decades, planners and government officials touted the Urban-Rural Demarcation Line, or URDL, as a milestone in suburban land management. No other suburban county in Maryland has anything like it.

The URDL is the reason that drivers traveling northbound on Interstate 83 see nothing but green forests and farms for more than 10 miles until they reach the Pennsylvania line — and sprawl after they cross it. It’s why Baltimore County’s valleys — Greenspring, Caves, Worthington — look much the way they did a half-century ago, and horses still roam not 10 miles from the Baltimore City line.

This preserved land protects the water supply for millions of people. Within the line, homes rely on public water and sewer. Outside of it, there are some hookups to the sewer system, but most homes are on septic systems and use wells. With the land largely preserved, Baltimore’s water supply is protected.

The preserved land — almost 70,000 acres, according to the county — also keeps stormwater runoff from development out of the Gunpowder River. The Gunpowder feeds the Loch Raven Reservoir, which supplies much of the city and county with their water. The river also is a tourism boon, drawing fishermen from all over the world for the clean, cold water and the trout that call it home.

But the URDL has a downside. Almost all new housing development gets pushed into the county’s bottom third, which already is crowded and expensive. And the county has promised to build even more housing — 1,000 affordable units before March 2028 — in an agreement to settle a federal housing lawsuit.

For years, west and east side advocates have grumbled that their communities bear the brunt of these new developments, which contribute to crowded roads and schools. At least one County Council candidate, Sharonda Huffman, is asking about the wisdom of holding the line.

“You see this?” Huffman asked at a December campaign event, waving at the demarcation line on a map. “That’s made up. … The planning department kept telling me, ‘Yeah, you’re not allowed to build there.’ Who said that? You can just change the law if we’re facing a housing crisis.”

Comments like Huffman’s helped convince Councilman David Marks to try to change the law, though not in the way Huffman suggested. The Eastside Republican is introducing legislation Monday night that would ask voters to change the county charter and make it more difficult to encroach on the URDL.

Currently, a change to the URDL, not lightly undertaken, requires four of seven County Council votes and a review by the planning board.

Marks’ legislation would require a “majority plus one” as well as planning board approval and the consent of the council member in whose district the change would occur. The URDL is mostly in Councilman Wade Kach’s district, and Kach has long called the URDL “sacrosanct.” But Kach, a moderate Republican, is retiring. Entering the race to replace him is Del. Nino Mangione, who hails from an influential Baltimore County developer family.

The new council will include nine members, so changes to the URDL would require six votes under Marks’ legislation.

If council members pass the bill, the measure would go to the voters in 2026. If they pass it, the charter change would take effect soon after.

Marks has titled the bill the Baltimore County Farmland Preservation Act. Contrary to what Huffman stated , Marks said, the line was not “made up.” It was the subject of intense study by Baltimore County land-use planners who examined farmland, small streams, rivers and valleys to determine a path forward that would conserve the most important ecological areas.

Preservationists already have lined up in support.

“Baltimore County’s agricultural, water and rural open spaces are a resource worth protecting,” wrote Angelo Otterbien, president of the Sparks-Glencoe Community Planning Council, which is outside the URDL and in part of the county where new development is restricted. “We see no more important safeguard to protecting land and the watershed than keeping the URDL fixed where it is.”

Bryan Fischer, chair of the Baltimore County Historic Trust, also supports holding the line.

“Any alterations to this important safeguard must be made with extreme care if at all. Once an historic landscape is altered by development, it is gone forever,” he wrote to Marks.

Fischer said he was in “whole-hearted” support of the legislation.

Ryan Coleman, president of the Randallstown NAACP, said he supports protecting the county’s land and water. But he thinks the URDL may need to be tweaked so that all communities are shouldering the burden of affordable housing — especially because residents who need that housing come from all communities.

“The URDL was innovative back in 1969. It’s not that innovative in 2025,” he said.

Marks said over the weekend that he believes he has the five votes he needs to put a charter amendment before voters. The council will discuss the bill several more times and likely vote in a few weeks.