The breadth at the widest point, from Tanjong Pen-unjut in Trengganu to Tanjong Hantu in the Dindings territory, is about 200 m.
On the east coast the principal streams are the Petani, Telubin, Kelantan, Besut, Trengganu, Dungun, Kmamun, Kuantan, Pahang, Rompin, Endau and Sedeli, all guarded by difficult bars at their mouths, and dangerous during the continuance of the north-east monsoon.
The Trengganu river is obstructed by impassable rapids at a distance of about 30 m.
Only two tin lodes are worked, however, and both are situated on the east coast, the one at Kuantan in Pahang, the other at Bandi in Trengganu territory.
Under British protection (since 1909) are Kelantan, Trengganu, Kedah and Perlis (Palit).
By a treaty made between Great Britain and Siam in 1902 the northern Malay states of the peninsula were admitted to lie within the Siamese sphere of influence, but by a treaty of 1909 Siam ceded her suzerain rights over the states of Kelantan, Trengganu, Kedah and Perlis to Britain.
These negotiations continued all through 1908 and resulted in a treaty, signed and ratified in 1909, by which Siam ceded to Great Britain her suzerain rights over the dependencies of Kedah, Kelantan, Trengganu and Perlis, Malay states situated in southern Siam just north of British Malaya, containing in all about a million inhabitants and for the most part flourishing and wealthy, and obtained the practical abolition of British jurisdiction in Siam proper as well as relief from any obligations which, though probably very necessary when they were incurred, had long since become mere useless and vexatious obstacles to progress towards efficient government.