The Homer Tunnel, some 60 chains long, pierces the Main Divide at the head of Hollyford Valley; it is 11 miles from Milford Sound, to which it affords the only road access. In 1889 W. H. Homer discovered Homer Saddle at the head of the Hollyford Valley and suggested the possibility of a tunnel through the ridge below the saddle. The idea of a through-road and a tunnel was later proposed by J. Cockburn to the Southland Progress League in 1929. Excavation was started in 1935 and the tunnel pierced in 1940. Work was suspended on the road and tunnel during the Second World War, and in 1945 a very large avalanche severely damaged the eastern tunnel portal. Work was resumed after the war and the tunnel was officially opened for road traffic in 1953.
The tunnel, which has a slight gradient towards the western portal, is in itself a spectacular sight, and visitors find much to see during stops at either portal.