Direct Contiguity, 1816-2006 (v3.1)

The Direct Contiguity data set registers the land and sea borders of all states since the Congress of Vienna, and covers 1816-2000. Version 3.0 of the Correlates of War Direct Contiguity data identifies all direct contiguity relationships between states in the international from 1816 through 2000.

The classification system for contiguous dyads is comprised of five categories, one for land contiguity and four for water contiguity. Land contiguity is defined as the intersection of the homeland territory of the two states in the dyad, either through a land boundary or a river, such as the Rio Grande in the case of the US-Mexico border. Water contiguity is divided into four categories, based on distances of 12, 24, 150, and 400 miles.