The individual and collective history and character of the Three Towns is outlined, with special reference to factors affecting their potential as library environments. The libraries are then presented by type, each type being introduced by.n appropriate sketch of the national setting and specialist local background, followed by accounts of individual libraries. The libraries are mostly post-1800, and the main types are: commercial subscription, private subscription, literary and philosophical, mechanics' institutes, cooperative, rate-supported, school, scientific, medical, law and naval libraries. The general conclusions reached are: that the Three Towns contained a number of libraries which were amongst the earliest of their type; that they also contained good examples of types of libraries which have received comparatively little professional attention, such as cooperative and naval libraries; and that W.B.K. Wright, the Borough Librarian of Plymouth 1876-1915, was one of the most important provincial founder-members of the Library Association and deserves greater recognition for his work in promoting the public library movement. At the regional level, it is concluded that the Three Towns, led by old Plymouth, often pioneered library developments in Devon and Cornwall. At the local level, it is concluded that although the Three Towns were contiguous and occupied only a small geographical area, nevertheless they did exhibit some interesting differences in their respective library developments which can be attributed to specialist factors in their individual histories and characters. For all of these reasons, the pre-1914 library history of the modern City of Plymouth is significant and deserves to be better known in the professional literature.