The earliest European settlers came to the area in the 1730s. They were mostly Scotch-Irish who came to America to escape famine in Ireland. In the early days, parts of what are now Adams and York Counties were claimed by both Maryland and Pennsylvania. One such area was "Carroll's Delight," which was chartered in 1735 by Maryland, and covered 5,000 acres in the vicinity of Fairfield and Hamiltonban. The Pennsylvania Provincial Assembly created York County in 1749, which included all of what is now Adams County. The 1749 charter created "Hamilton's Bann" township, which then covered what are now Hamiltonban, Liberty and Freedom Townships as well as Fairfield and Carroll Valley Boroughs.The largest settlement in Hamiltonban, Fairfield, was laid out on 247 acres of land in Carroll's Delight purchased by John Miller in 1755. Squire Miller quickly sold off lots for the purpose of agriculture, and built a stone manor house in 1757, and licensed it as a tavern in 1786.

Early in the day on July 3rd, 1863, Jones' Brigade of Stewart's Cavalry Division of the Confederate Army of Northern Virginia fought a bloody battle with the 6th U.S. Cavalry on Carroll's Tract Road, just 2 miles north of Fairfield. The Union Cavalry was driven back to Emmitsburg, and Jones' Brigade remained in Fairfield, protecting the left flank of the Confederate Army during Pickett's Charge on the decisive day of the Battle of Gettysburg. Jones Brigade encamped at Fairfield that night, and the next day, one of two major columns of the Army of Northern Virginia began its retreat through Fairfield, up Iron Springs Road, and over South Mountain through Monterey Gap (now within Borough of Blue Ridge Summit). The other column, with Lee's wagons, supplies, and wounded retreated through Cashtown towards Chambersburg.In 1896, Fairfield was incorporated as a borough, with it's own governing body separate from Hamiltonban. Carroll Valley Borough was chartered from Hamiltonban and Liberty Townships on September 30, 1974.