The A625 previously ran, undiverted, between Castleton and Chapel-en-le-Frith, winding its way up the south face of Mam Tor—replacing a much earlier route through the Winnats Pass.

This section of the road proved highly prone to landslides, especially after periods of heavy rain, and was in constant need of repair.

This section of the road was first constructed in 1819 by the Sheffield & Chapel-en-le-Frith Turnpike Company using spoil from the nearby Odin Mine.

Also known locally as "The New Road", the new section was set at an easier gradient than the earlier Winnats Pass route and crossed the Mam Tor landslide.

Additional road works were carried out regularly, when wet years led to further landslides.