The Lowlands is not an official geographical or administrative area of the country. There are two main topographic regions: the Lowlands and the Southern Uplands. The term "Lowlands" mainly refers to the Central Lowlands. However, in normal usage it refers to those parts of Scotland not in the Highlands (or Gàidhealtachd). The boundary is usually considered to be a line between Stonehaven and Helensburgh (on the Firth of Clyde). The Lowlands lie south and east of the line. Note that some parts of the Lowlands (such as the Southern Uplands) are not physically "low," Merrick for example reaching 2,766 feet, while some areas indisputably in the Highlands (such as Islay) are low-lying.
In geological terms, the dividing line between Lowlands and Highlands is the Highland Boundary Fault. There was also a legally defined Highland Line in the post-Culloden years, part of the measures taken to suppress Gaelic culture.
For other purposes, the boundary varies; but if the Boundary Fault is used, then the traditional Scottish counties entirely in the Lowlands are: Ayrshire, Berwickshire, Clackmannanshire, Dumfriesshire, East Lothian, Fife, Kinross-shire, Kirkcudbrightshire, Lanarkshire, Mid-Lothian, Peeblesshire, Renfrewshire, Roxburghshire, Selkirkshire, West Lothian and Wigtownshire.
Geographically, Scotland is divided into three distinct areas: the Highlands, the Central plain (Central Belt), and the Southern Uplands. The Lowlands cover roughly the latter two. The northeast plain is also "low-land," both geographically and culturally, but in some contexts may be grouped together with the Highlands.
The term Lowlands is sometimes used in a more restricted sense to refer specifically to the Midland Valley. Much of this area, which has a characteristic structure of sedimentary rocks with coal deposits, lies within the basins of the Rivers Forth and Clyde. Historically, this valley has been the most agriculturally productive region of Scotland. During the 19th and early 20th centuries, coal deposits promoted concentrated industrial activity and urbanization in the Midland Valley, where 80 percent of the population of Scotland now live. While coal mining and other heavy industry have declined in the region, it remains at the centre of the Scottish economy, with electronics and computer manufacture and service sectors such as telecommunications, computer software, and finance.