"A market town, the head of a Union, and a parish ..... chiefly in the Uchdulas division of the hundred of Isdulas, county of Denbigh; 20 miles (W by S) from Denbigh, 26 (W by N) from Ruthin, and 217 (NW by W) from London; containing 3601 inhabitants. ..... The town is pleasantly situated on the eastern bank of the river Conway, four miles to the north of the road to Holyhead, and in the spacious and beautiful vale of Llanrwst, environed by majestic and well-wooded hills. ..... The parish is upwards of forty miles in circumference." [A Topographical Dictionary of Wales, 1833 & 1849, Samuel Lewis]
The ancient parish of Llanrwst was of great extent. It comprised the township of Gwydir, in Caernarfonshire (the area of which was 7694 acres); and a number of townships in Denbighshire, with an area of 15,298 acres. These townships were Cilcennis, Tre'r Dre Isaf, Tre'r Dre Uchaf, Garthgyfannedd, Mathebrwd, Tybrith Isaf, Tybrith Uchaf, and Garth Garmon, in Denbighshire.
In 1866, a portion of the township of Gwydir was transferred by an Order in Council to the parish of Capel Curig, in Caernarfonshire.
Tybrith Ucha and Garth Garmon had for many years operated, unofficially, as the parish of Capel Garmon; and this was made official in 1927.