When the emigrants crossed the Missouri River, they left behind the United States. They left after months of careful planning with, they hoped, everything they would need for their four to six months of westward travel. And, if they were lucky, their health was good and their animals sure-footed. Now with the grass high enough to ensure ample forage and a strange mix of anticipation and trepidation, they bid farewell to family and friends, probably forever, and set out to find their new home.      It usually didn’t take long for the emigrants to realize that they had made at least one miscalculation when it came to putting together their equipage. You could try to trade with other emigrants for the goods you needed. But if no one had any to spare, your next opportunity to purchase supplies would be the small trading posts that sprang up along the trails. Chief among these were Wyoming’s Fort Laramie and Fort Bridger along with Fort Hall in Idaho.       Forts offered more than simply an opportunity to purchase new supplies and rest in relatively luxurious surroundings for a few days. From the forts, you could send a letter to your loved ones. If, for any number of reasons, you had become disgruntled with your traveling companions, you could join another wagon train. Medical assistance, always scant along the trails, improved somewhat at the forts. Many travelers found messages waiting for them from friends or family who had already passed by the fort. More than a few emigrants used a stay at Fort Laramie to reassess their plans and turn back.       But perhaps the most important commodity available at the forts was information. Those who lived at these remote outposts usually had invaluable advice to share about the conditions ahead. And while, today, we think only of the emigrants heading west, the trails almost always carried travelers heading in both directions. Those already settled in the west would often take advantage of the summer season to head east, to visit family or to obtain special supplies or to escort others back to the "land of milk and honey." These eastern travelers, having just passed through the region, could supply first-hand information about the conditions ahead.       Despite all these inducements, many travelers chose to pass by the forts. Getting to Fort Laramie required an extra river crossing and the route to Fort Bridger required a significant detour following the opening of the Sublette Cutoff. Yet, if you needed the supplies or the rest stop or the information available, you had few choices and the trail forts represented a true oasis in your long journey