The Castlereagh Highway runs from Lithgow to St George. The highway starts 10 kilometres north of Lithgow from the junction with the Great Western Highway. It runs in a north-westerly direction until it joins with the Golden Highway through Dunedoo. It then continues northwest from Dunedoo until it reaches the village of Hebel at the Queensland/New South Wales border. It continues through Queensland until it meets the Carnarvon Highway east of St George. It is 822 kilometres long and a 9.5 hour drive. The kilometres mentioned in this website are approximate only