The Lancashire and Yorkshire Railway locomotive works were originally at Miles Platting, Manchester.
Hurst left to join the North British Railway in 1854 and Jenkins continued on his own.
Each can cover several similar varieties, e.g. all the non-superheated 0-8-0s are Class 30 During this period the Horwich Works was under construction and apart from a few built at Miles Platting, engines came from outside manufacturers.
From 1889 Horwich Works was completed and from that time all engines were constructed there.
The "number only" classes are those introduced by George Hughes in 1919 and shown in the L&YR working timetable appendix of 1921.