Travelers gathered and ignited dried cow dung to cook their meals. These burned fast in a breeze, and it could take two or more bushels of chips to get one meal prepared. Those traveling south of the Platte crossed the South Platte fork at one of about three ferries (in dry years it could be forded without a ferry) before continuing up the North Platte River Valley into present-day Wyoming heading to Fort Laramie. Before 1852 those on the north side of the Platte crossed the North Platte to the south side at Fort Laramie. After 1852 they used Child's Cutoff to stay on the north side to about the present day town of Casper, Wyoming, where they crossed over to the south side. Notable landmarks in Nebraska include Courthouse and Jail Rocks, Chimney Rock, Scotts Bluff, and Ash Hollow with its steep descent down Windlass Hill over the South Platte. Today much of the Oregon Trail follows roughly along Interstate 80 from Wyoming to Grand Island, Nebraska. From there U.S. Highway 30 which follows the Platte River is a better approximate path for those traveling the north side of the Platte. The National Park Service (NPS) gives traveling advice for those who want to follow other branches of the trail. Because of the Platte's brackish water, the preferred camping spots were along one of the many fresh water streams draining into the Platte or the occasional fresh water spring found along the way. These preferred camping spots became sources of cholera in the epidemic years (1849–1855) as many thousands of people used the same camping spots with essentially no sewage facilities or adequate sewage treatment. One of the side effects of cholera is acute diarrhea, which helps contaminate even more water unless it is isolated and/or treated. The cause of cholera (ingesting the "Vibrio cholerae" bacterium from contaminated water) and the best treatment for cholera infections were unknown in this era. Thousands of travelers on the combined California, Oregon, and Mormon trails succumbed to cholera between 1849 and 1855. Most were buried in unmarked graves in Kansas, Nebraska and Wyoming. Although also considered part of the Mormon Trail, the grave of Rebecca Winters is one of the few marked ones left. There are many cases cited involving people who were alive and apparently healthy in the morning and dead by nightfall. A branch of the Oregon trail crossed the very northeast corner of Colorado if they followed the South Platte River to one of its last crossings.