carson have become national folk heroes. after two successful expeditions to blaze the oregon trail. >> they were the first people to figure out where they could forge rivers, what was the safest routes so you didn't have to climb mountains and they led all of the mountaineers. >> the path finder and kit carson was his trustee scout. >> john fremont is a darling but the truth path finder is kit carson. today they fueled the western expansion but soon their mission to map the western territories will take on an even greater significance. >> on their third outing, an unexpected dispatch arrives from the white house. >> it's from president polk and