with information from "British Colonial Stamps in Current Use September 1949" H.M. Stationery Office
The territory known as the Gambia, part colony and part protectorate, forms an enclave in the French colony of Senegal. About 12 miles wide, it extends some 250 miles along either bank of the great West African river Gambia, about 13 degrees north of the Equator.
The population of the Colony (1944) was 21,152 and that of the Protectorate (1946) 228,114.
There are 4 Post Offices, situated at Bathurst, Kuntaur, Georgetown and Basse. Postal Agencies exist at Cape St. Mary, Brikama Kaur, Bansang and Kristi Kunda, and there is a Travelling Post Office aboard H.M.C.S. "Prince of Wales".
This sounds like a great little collecting field for a one or two frame exhibit. Bathurst was also a significant jumping off point for southern route transatlantic flights to Brazil using catapault ships (the Westfalen and the Schwabenland), and four shuttle flights of the Graf Zeppelin in 1935-36 when both catapult ships were temporarily withdrawn from service for repairs. No landings were made by the Graf Zeppelin at Bathurst; mail was dropped and picked up by long ropes. But that's a subject for another article.
Sounds like a philatelically fascinating and challenging place!