This thesis assesses the evolution of historic maps of Ireland using Geographic Information Systems (GIS) and quantitative approaches. Each of nineteen early modern maps dating to the sixteenth and early seventeenth centuries (c.1530 – 1610), a formative period of Irish cartographic history, was analysed to statistically assess the relative positional accuracy of places included on the cartography. Building upon previous studies of analysing cartographic veracity using quantitative approaches, notably Tobler's (1994) bidimensional regression technique, it is the first of its kind to apply these techniques to a series of historic maps. The aim is to test these approaches systematically and critically, compare the statistical techniques, and offer insights into their analytical potential in the history of cartography and historical geography. The thesis also aims to enhance our understanding of the evolution and development of maps and map-making during an age often regarded as revolutionary in scientific cartography in Europe. The study highlighted two main historical and cartographic groups; (I) earlier maps of Ireland created prior to Lythe’s survey cartography in which mapmakers appeared to take a more artistic rather than a ‘measured’ approach to mapping and; (II) maps created subsequent to Lythe’s and of generally higher cartographic precision in illustrating the island's geography. Enduring map ‘errors’ that survived through to the seventeenth century are discussed, and illustrate that the development of maps of Ireland did not progress in a linear fashion. Map lineage was complex, and plagiarism between mapmakers was rife with one map, by Robert Lythe (PHA 9581, c.1571), shown to form the basis for many subsequent maps. The methodology developed in this thesis is a fundamental addition to early map research, by adding to key debates in the history of cartography concerned with how early maps developed and evolved, and providing new insights on Ireland’s early cartography.