Continuing upstream from Casper, the North Platte bends to the southwest headed for the Colorado Rockies.
About 50 miles (80 km) southwest of Casper the North Platte is joined by the Sweetwater River (Wyoming).
This river junction is deep in a canyon now filled by the Pathfinder Reservoir.
The trail crossed over the North Platte by ferry and later by bridge.
Some of the original immigrant travelers proceeded several miles along the North Platte River to Red Buttes, where a bend in the river formed a natural amphitheater dominated by red cliffs on the hill above.
The cold North Platte was easier to ford here for those who were unwilling or unable to pay to cross at one of the ferries downstream.
This was the last good camp spot before leaving the river and entering the water less stretch between the North Platte and the Sweetwater River.
From here the settlers entered a difficult portion called Rock Avenue which moved from spring to spring across mostly alkaline soil and steep hills until it reached the Sweetwater River.
Later settlers who had crossed to the northern side of the river at Casper would come to favor a route through a small valley called Emigrant Gap which headed directly to Rock Avenue, bypassing Red Buttes.

Upon arrival in the Sweetwater valley, the trail encounters one of the most important landmarks on the trail, Independence Rock.
Independence Rock was named by Jedediah Smith and party when they first observed it in 1824 on July 4--Independence Day in the United States.
Jedediah and his fellow trappers rediscovered South Pass and the Sweetwater River in 1824.
Immigrants also tried to reach Independence Rock on July 4 in order to help ensure that they will be at their destinations in California or Oregon before the winter snows came and closed the trails.
Many of the travelers left their names on the rock, either carved or painted on with axle grease.
It is estimated that more than 50,000 signatures were inscribed on Independence Rock.
Other notable landmarks along the Sweetwater valley include Split Rock, Devil's Gate and Martin's Cove, where, in October to November 1856, the Martin Handcart Company was stranded by an early heavy snow and a late start and about 145 died before they were rescued by the rescue parties (about 250 wagons with supplies and help were dispatched from Utah) sent by Brigham Young from Salt Lake City.

The immigrant trail continues west along the Sweetwater River eventually crossing the meandering river nine times, including three times within a 2 miles (3.2 km) section through a narrow canyon in the Rattlesnake Hills.
Prior to the 6th crossing, the trail crossed an unusual location known as Ice Slough.
A covering of peat like vegetation grew over a small stream.
The stream froze in winter and didn't thaw until early summer due to the insulating layer of vegetation.
The ice was a welcome treat for settlers who were often enduring temperatures over 90 °F (32 °C) in July.
The trail crosses the Sweetwater three more times and encounters a large hill known as Rocky Ridge on the northern side of the river.
This barren and rocky section lasted almost 12 miles (19 km), and was considered a major obstacle in the trail.
The same storm in November 1856 that debilitated the Martin Handcart Company also stranded the Willie Handcart Company on the eastern side of the ridge.
Before rescuers could arrive, 56 people died in freezing temperatures out of a company of about 600.
Following Rocky Ridge, the trail descends one more time into the Sweetwater valley to the ninth and final crossing of the Sweetwater at Burnt Ranch.

In 1853, a new route named Seminoe cutoff was established on the southern side of the river.
It was named after trapper Basil LaJeunesse who was referred to as Seminoe by the Shoshone Indians.
The Seminoe cutoff split from the main trail at the 6th crossing and rejoined it at Burnt Ranch, bypassing both Rocky Ridge and four of the river crossings, which was an advantage in the early spring and summer during high runoff.
The route was used extensively in the 1850s, especially by
Continuing upstream from Casper, the North Platte bends to the southwest headed for the Colorado Rockies. About 50 miles (80 km) southwest of Casper the North Platte is joined by the Sweetwater River (Wyoming). This river junction is deep in a canyon now filled by the Pathfinder Reservoir. The trail crossed over the North Platte by ferry and later by bridge. Some of the original immigrant travelers proceeded several miles along the North Platte River to Red Buttes, where a bend in the river formed a natural amphitheater dominated by red cliffs on the hill above. The cold North Platte was easier to ford here for those who were unwilling or unable to pay to cross at one of the ferries downstream. This was the last good camp spot before leaving the river and entering the water less stretch between the North Platte and the Sweetwater River. From here the settlers entered a difficult portion called Rock Avenue which moved from spring to spring across mostly alkaline soil and steep hills until it reached the Sweetwater River. Later settlers who had crossed to the northern side of the river at Casper would come to favor a route through a small valley called Emigrant Gap which headed directly to Rock Avenue, bypassing Red Buttes.
Upon arrival in the Sweetwater valley, the trail encounters one of the most important landmarks on the trail, Independence Rock. Independence Rock was named by Jedediah Smith and party when they first observed it in 1824 on July 4--Independence Day in the United States. Jedediah and his fellow trappers rediscovered South Pass and the Sweetwater River in 1824. Immigrants also tried to reach Independence Rock on July 4 in order to help ensure that they will be at their destinations in California or Oregon before the winter snows came and closed the trails. Many of the travelers left their names on the rock, either carved or painted on with axle grease. It is estimated that more than 50,000 signatures were inscribed on Independence Rock. Other notable landmarks along the Sweetwater valley include Split Rock, Devil's Gate and Martin's Cove, where, in October to November 1856, the Martin Handcart Company was stranded by an early heavy snow and a late start and about 145 died before they were rescued by the rescue parties (about 250 wagons with supplies and help were dispatched from Utah) sent by Brigham Young from Salt Lake City.
The immigrant trail continues west along the Sweetwater River eventually crossing the meandering river nine times, including three times within a 2 miles (3.2 km) section through a narrow canyon in the Rattlesnake Hills. Prior to the 6th crossing, the trail crossed an unusual location known as Ice Slough. A covering of peat like vegetation grew over a small stream. The stream froze in winter and didn't thaw until early summer due to the insulating layer of vegetation. The ice was a welcome treat for settlers who were often enduring temperatures over 90 °F (32 °C) in July. The trail crosses the Sweetwater three more times and encounters a large hill known as Rocky Ridge on the northern side of the river. This barren and rocky section lasted almost 12 miles (19 km), and was considered a major obstacle in the trail. The same storm in November 1856 that debilitated the Martin Handcart Company also stranded the Willie Handcart Company on the eastern side of the ridge. Before rescuers could arrive, 56 people died in freezing temperatures out of a company of about 600. Following Rocky Ridge, the trail descends one more time into the Sweetwater valley to the ninth and final crossing of the Sweetwater at Burnt Ranch.
In 1853, a new route named Seminoe cutoff was established on the southern side of the river. It was named after trapper Basil LaJeunesse who was referred to as Seminoe by the Shoshone Indians. The Seminoe cutoff split from the main trail at the 6th crossing and rejoined it at Burnt Ranch, bypassing both Rocky Ridge and four of the river crossings, which was an advantage in the early spring and summer during high runoff. The route was used extensively in the 1850s, especially by 
California Trail