The Great Northern Railway (GNR) Small Boiler Class C1 is a class of steam locomotive, the first 4-4-2 or Atlantic type in Great Britain. They were designed by Henry Ivatt in 1897. In total 22 were built between 1898 and 1903 at Doncaster Works. The class were commonly known as 'Klondykes' [sic], after the 1897 Klondike gold rush. They could reach speeds of up to 90 mph (145 km/h). They were also known as Small Atlantics.