Its older names, Athleague and Ballyleague, derive from the Irish Béal Átha Liag, meaning the mouth of the ford of the stones, and the place earned that description honestly: a causeway was constructed across the river in the year 1000, followed by timber bridges in the mid-12th century. The town known today carries the name of Sir George Lane, who held the lands in 1664 when they were erected into the manor of Lanesborough, but the settlement he gave his name to had already been through several cycles of construction, destruction, and abandonment before he arrived.

The crossing sat on the border between the early medieval kingdoms of Connacht and Midhe, and later between the modern counties of Longford and Roscommon, which meant it was always contested. Walter de Lacy began a castle here in 1172 but was forced to abandon it by Cathal Crobderg O Conncobair, King of Connacht. The structure eventually built in 1227 by Geoffrey de Marisco, the Irish Justiciar, the crown's chief legal and administrative officer in Ireland, seems to have prompted the growth of a small town around it; a charter of borough status was granted before 1235. The de Verdon family inherited the settlement and in 1284 Theobald de Verdon secured a charter for a weekly market, suggesting at least some commercial ambition. It did not last. By 1332, in the partition of his lands following his death, 18 carucates of land in the town were recorded as being worth nothing at all, waste and uncultivated for lack of tenants. The Anglo-Norman experiment here had quietly collapsed. Plantation-era figures moved in during the early 17th century, among them Sir Patrick Barnewell, who built what contemporary sources called a fair and strong fort, probably on the site of the levelled medieval castle. By the 1650s the Down Survey map showed a modest cluster of buildings around the fort on the Longford side, with a separate castle on the Roscommon bank. A visitor in 1682, Nicholas Dowdall, described fine stone houses and a church with a tall steeple, its churchyard walled about, giving an impression of modest but settled prosperity.

What makes the place quietly strange today is the near-total disappearance of all of this. No trace of the 17th-century buildings survives in the modern streetscape. The castle and fort have been levelled. Scholars are not even certain whether the medieval borough stood on the Longford bank at all; it may have been on the Roscommon side, in the vicinity of Ballyleague Castle across the water. The one main street of the plantation-era town, running roughly north-northwest to south-southeast with long property plots stretching off either side, may be the only structural inheritance still legible in the layout of the modern town, though even that is uncertain. A place that spent centuries as a contested crossing point, a garrisoned bridge-town, and a twice-chartered borough has left almost nothing above ground to show for it.