The Westlands is one of several names given to the continent or subcontinent that stretches from the Aiel Waste to the Aryth Ocean, and from the Great Blight to the Sea of Storms. It forms the westernmost part of one large landmass that also incorporates the Aiel Waste and the land of Shara, as well as a number of offshore islands belonging to the Sea Folk.
The Westlands stretches for roughly 3,500 miles from the Aiel Waste to the Aryth Ocean and is mostly temperate, with hot summers in the southern regions and icy winters in the north. The continent consists of several large plains (notably Almoth Plain, the Plains of Maredo, Caralain Grass, and the Plain of Lances) divided by extensive forests, marshes, and several major mountain ranges, most notably the Mountains of Mist which divide the western coastal regions from the continental interior.
The continent is dominated by two extensive river networks. The larger consists of the River Manetherendrelle and its major tributary, the Arinelle. This network rises in the Mountains of Dhoom in the far north and is navigable almost from the Blight to the river mouth at Illian. The River Erinin flows out the Spine of the World just south of the Niamh Passes westwards before turning south for two thousand miles, eventually reaching the sea at Tear. Although not as extensive as the Arinelle-Mantherendrelle network, the Erinin is by far the longer single river and sees much more traffic, as it passes through two of the busiest cities on the continent.
There are currently fourteen nations in existence in the Westlands: Altara, Amadicia, Andor, Arad Doman, Arafel, Cairhien, Ghealdan, Illian, Kandor, Murandy, Saldaea, Shienar, Tarabon, and Tear, as well as four major city-states: Falme, Far Madding, Mayene, and Tar Valon. In previous eras, every part of the land was claimed by one nation or another, but in the modern era there are vast stretches of the continent which are given over to wilderness and are rarely traveled.
The main continent does not posses one single unified name, and is referred to by a variety of titles within the books and fandom. 'Randland' is a common fan term, but is not used in the books themselves. The World of Robert Jordan's The Wheel of Time uses the term 'The Land', but this is also not used in the books themselves. The term 'Westlands' originates from The Wheel of Time Roleplaying Game and was subsequently used by Robert Jordan in occasional interviews. The only single name used frequently in the novels themselves is 'the wetlands', the Aiel term for the lands west of the Spine of the World as they are much more fertile than the Waste.
Although no scale appears on the maps in the books themselves, a scale did appear on the world map on page 146 of the guidebook accompanying the series, The World of Robert Jordan's The Wheel of Time. The scale on this map suggests that the distance from the Aryth Ocean to the Spine of the World exceeds 3,000 miles. This concurs with the designers who worked on The Wheel of Time Roleplaying Game, who suggested a scale of 1"=400 miles on the color endpaper maps in the hardback editions of the books. By their calculations, the Westlands therefore measures roughly 3,500 miles from the west coast to the Spine of the World, making it approximately the size of the United States of America. In an interview, Robert Jordan seemed to concur, suggesting it was almost 4,000 miles from the Spine to the ocean.
A reliable way of measuring the maps was produced in the novel New Spring, which gave the straight-line distance from Tar Valon to the sea south of Tear as 400 leagues (1,600 miles). Other distances in the novels include 600 miles for Cairhien to Caemlyn, 100 miles for Emond's Field to Baerlon, 900 from Tear to Aringill, 800 miles for the length of coastline between Ebou Dar and Illian, and 1,500 miles for Cairhien to southern Ghealdan (although another distance is given of 500 leagues - 2,000 miles - for Kinslayer's Dagger to northern Amadicia).
At the 'present' time in the novels (the end of Knife of Dreams), the southwest of the continent is held by the Seanchan, while the northeast is held by forces loyal to the Dragon Reborn. The allegiance of the Borderlands in the north is unknown.
The islands of the Aile Somera and Aile Jafar, plus the kingdoms of Tarabon, Amadicia, and Altara, are held by the Seanchan invaders. Their influence also extends into Almoth Plain and Ghealdan, and there has been fighting with the armies of Arad Doman. The Aiel Waste, Cairhien, Tear, and Illian are held by the Dragon Reborn, with a strong influence in eastern Andor.