Historically the London & North Western Railway, evolving to the West Coast Main Line connecting London with Scotland.
MAIN LINE: Euston-Milton Keynes
4 tracks Euston-Milton Keynes
From east to west, pairs of tracks identified as Slow, Fast.
Separate 2 track DC Electric Line parallels to east, Camden Junction to Wembley, and parallels to west, Wembley to Watford Junction. DC Electric Line also used by London Underground Bakerloo Line north of Queens Park.
St. Albans (Watford Junction-St. Albans Abbey/1 track)
All lines 2 tracks unless noted. All lines AC electrification unless noted, including DC Electric Line DC electrification.
Number Of Platforms/Tracks: 18
Platforms numbered east to west
North of Euston Station, the DC Electric Line diverges from the Slow Line.
Wikipedia link containing further station information and history.