Council leaders from both sides of the border between England and Wales have signed a new, economic deal, which they say is the first of its kind.
The Marches Forward Partnership includes Herefordshire, Shropshire, Powys and Monmouthshire. Together they have a population of more than 750,000.
Politicians say the new agreement will give the rural counties a voice on the national stage, as they jointly bid to government for investment for transport, tourism, skills and the environment.
The partnership has already secured a £3.25m grant to improve 5G reception, and has been welcomed by the Secretary of State for Wales David TC Davies.
A memorandum of understanding between the local authorities was signed at Hay Castle, in the border town of Hay-on-Wye, on Friday.
Council leaders said the Welsh town, which has a Herefordshire postcode, typified how the national border should not impede residents' day-to-day lives.
"We're connected. We've been connected for millennia," said Mary Ann Brocklesby, the Labour and Co-operative leader of Monmouthshire Council.
"To have national borders is a significant thing in its own right," said the Conservative leader of Herefordshire Council Jonathan Lester.
"But when it comes to daily life, they play a very small part," he said. "Let's hope it's the beginning for getting more for our region."
The agreement comes after 18 months of talks between the local authorities, which will still retain their independence.
Council leaders said they would not copy the West Midlands in having a directly elected mayor and the scheme would not cost taxpayers extra money.
Shropshire Council's Conservative leader, Lezley Picton, said the deal would ensure the rural Marches could better compete with big cities for government investment.
"The difficulty we have sometimes is that when government money comes out, say for levelling up, it goes to urban areas, " she said.
"Our stronger voice - much, much stronger with four authorities - is saying 'do not overlook the rural areas'."
The Secretary of State for Wales, David TC Davies, called the new partnership "ground-breaking", and said it had the full support and backing of the UK government.
The new agreement was also welcomed by the transport minister, and Herefordshire MP, Jesse Norman.
"What this does is to restore the idea of the Marches, which is a really historical idea," he said.
"I think there hasn't been enough communication between both sides... that they're doing so now is very exciting."