The source of the Tweed is at Tweed's Well in Peeblesshire just east of the border with Lanarkshire. It is east of the A701 road and there are forests north and south. Several small burns converge at Tweed' Well. This is very remote country although it is only a few miles north of the town of Moffat. The river runs north from here to Drumelzier where it begins to turn east towards Peebles. Most of the bridges between here and Drumelzier are rather basic, serving farms or remote dwellings.
A stone monument marks the Tweed's source alongside the A701 and relief carvings with text depict the river's progress to the North Sea.