They migrated up the valleys of the Trent and Tame from the Humber Estuary, and later formed Mercia. The Tame is generally considered to have two main sources; Willenhall and Oldbury. The tributaries arising in these locations are generally known as the Willenhall arm and the Oldbury arm of the Tame. However, some of its tributary streams, including Waddens Brook, rise as far to the west and north as Bilston and Wednesfield in the city of Wolverhampton. Much of the course of the river has been modified over the centuries, and the urban sections now run mainly through culverts or canalised channels. Both arms of the Tame flow through the Black Country to their confluence at Bescot, on the edge of Walsall. The northern arm is easily traced from Bentley, near Willenhall. However, the SMURF project traces it back as far as Stow Heath, near Bilston, where it is marked by a marshy patch at the northern end of the City of Wolverhampton College's Wellington Road campus; hence, SMURF uses the term "Wolverhampton arm" for this section of the Tame. Victorian Ordnance Survey maps trace the sources of the Tame further back, to the site of the old Stow Heath colliery, which is now Wolverhampton's East Park. The stream runs invisibly but generally north-eastward through Stowlawn, and then cuts across the southern edge of Willenhall, appearing briefly among the warehouses, and picking up reinforcement from the Waddens Brook, which originates in Wednesfield. It appears definitively at Watery Lane and Noose Lane, even more so at Bentley, where it runs southward through the industrial part of Bentley, before turning south-eastward, following a realigned course alongside and beneath the M6 motorway, to Bescot. The southern arm appears prominently close to Oldbury town centre, which gives it its name, but can be traced back to an industrial area at Titford, just west of the M5 motorway, between Whiteheath and Langley Green. It winds its way up through Langley and around the southern and eastern edges of Oldbury town centre, surfacing due south of Sandwell and Dudley railway station, from which point it remains mainly on the surface and is easily traced. Bearing generally north-westward, it skirts Brades Village and flows into Tipton.