The section of The National Gazetteer (1868) relating to Caernarvonshire - transcribed by Colin Hinson.
Tallis's Topographical Dictionary of England and Wales, published in 1860 in six vols, editor E. L. Blanchard.
See Welsh Family History Archive for all the excellent county maps (showing the hundreds) and the alphabetical gazetteer
From the preface;
"In the following pages will be found fully described the past history and present aspect of every place of any significance in England and Wales, forming a work of permanent importance to the commercial world, of ready service to the tourist of the day, and of constant interest to the general reader, who may derive from this source a large supply of entertainment, as well as of information for the amusement and instruction of a leisure hour."
Here is a map of the county with parish boundaries superimposed. Click on a section to bring up a bubble containing the parish name plus a link to its page
Map of Caernarfonshire in 1833 - Copied from the original in "A Topographical Dictionary of Wales" by Samuel Lewis 1833
Map of Carnarvonshire from the Report of the Boundary Commissioners for England and Wales. Printed by Eyre and Spottiswoode, London, 1885.
Gwynedd Family History Society have a diagram of the ecclesiastical parishes of Caernarfonshire - under Parishes. Some publications for specific parishes contained detailed maps of the local areas with individual house and street names.
Welsh county maps on the UK Genealogy Archives site
Report of the Boundary Commissioners for England & Wales - Map of Carnarvonshire 1885
Maps of Carnarvonshire on the Carnarvon Traders site
Tithe maps covering all of Wales have been digitized and indexed by the Cynefin Project. They can now be searched for free by Place/parish, occupier, landowner or field name using NLW Welsh Tithe Maps.