Rivers guided the emigrants throughout their westward journey. They provided essential water supplies and often offered relatively flat bottom lands along which to travel. Yet, no matter how benign they might appear, the rivers possessed their own treachery with which the emigrants had to cope.      The main artery guiding the emigrants into Wyoming was the great Platte River. Variously described as "a mile wide and an inch deep" or "too thick to drink and too loose to plow," the Platte became both the friend and the curse of the emigrants. In the years of the heaviest emigration, its shallow waters quickly became polluted from the wastes of people and animals. The polluted waters thus became a breeding ground for disease and, during several peak years, cholera ravaged the emigrants as they followed the Platte. In 1850, one emigrant described the Platte River Valley as "a vast graveyard."      Others made their camp alongside a gentle stream only to be awakened in the middle of the night by a raging river, bursting over its banks as the result of one of those common prairie cloudbursts. One unlucky emigrant remembered going to sleep in the wagon on dry land and being awoken by a rocking motion. Encamped on a seemingly stable sandbar, she now found herself floating aimlessly downstream.      The Sweetwater River, with its pleasing waters, welcomed the parched emigrants to central Wyoming. The waters were made all the sweeter by the previous days crossing from the Platte across the dusty, alkali plains. But what initially seemed most inviting about the river – its gentle, steady flows – soon turned into a lingering headache for the emigrants. The emigrants, unlike the Sweetwater River, were not content to meander gently over the landscape. To follow each bend might consume a day or more. Time being too precious for such nonsense, the emigrants crossed the Sweetwater once… And then again…and again…and again, until they had ultimately crossed it nine times. By then, most emigrants were happy to leave the Sweetwater behind even though that signaled the beginning of a long dry stretch over South Pass and on to the Green River.      Unlike the other rivers the emigrants encountered, the Green River was not going their direction. Instead, the swift-flowing river bisected the emigrant road and stopped the travelers cold in their tracks. To continue, they simply had to cross the deep, wide Green – that great, mighty river that would join the Colorado further downstream and continue on to carve the Grand Canyon.      Rivers – especially great rivers like the Platte and the Green – have a life of their own and they change daily. This unpredictably made river crossings one of the most dreaded of the challenges posed by the trails. People, fully loaded wagons, and reluctant cattle all had to be crossed. Smaller streams could be forded but that often entailed raising the wagon bed and the smallest misstep by drovers could send all the equipage rushing downstream. More than a few emigrants lost all the possessions when a wagon overturned. Many hundreds of others lost their lives.       Ferries represented a great advancement and when you found an established ferry with an experienced operator, the odds of making a safe crossing shot up considerably. Unfortunately, they were not cheap. Prices fluctuated based on conditions and, of course, the higher and swifter the river’s flow, the more an operator could, and did, charge. Moreover, a ferry could only handle so much traffic in a day and so emigrants often waited days to cross. Encampments of the emigrants waiting to cross often grew crowded and unsanitary, with little forage for the animals. But what choice did you have? If you were lucky, you had the money to pay the toll and the time to wait your turn. If you weren’t so lucky, your choices were bleak: try to ford, perhaps to ruinous end or trade away some essential to get the cash and watch yourself slip further and further behind on your schedule.      Because the rivers were there, the rivers weren’t going to part for you, and the trail continued on the other side. Drink from the cool clear river and praise it or cross its roiling waters and curse it. But make your peace with the rivers because they would be your friend and tormentor for months to come.      Today, massive water diversions through dams and irrigation projects have changed dramatically the character of Wyoming’s rivers.