At Dotsero (MP 342.0), altitude 6,155 ft., the present-day main line takes the Dotsero Cutoff to the north, following the Colorado River, and the Tennessee Pass line heads east at a wye, single track, CTC, speed limit 25 mph at the junction, following the Eagle River, bridging over it four times in a relatively short distance and then running along its south bank, past a detector at MP 339.4, Gypsum (MP 335.8), where the speed limit is 20 mph past the gypsum facilities on the south side, a detector at MP 335.7, the 7,760 ft. siding at Sage (MP 332.8 to MP 331.0), where the speed limit rises to 40 mph, a turn northeast past Eagle (MP 329.0) and a bridge to the north bank of the river, turning east-northeast to follow that bank, past a detector at MP 328.3, a detector at MP 328.1, Ortega, a detector at MP 325.5, Sherwood, and a detector at MP 321.8, turning east, bridging across the river, turning south to follow the river, and then east to bridge across it again to the 7,570 ft. siding at Wolcott (MP 319.0).
The line now turns curvily south-southeast, following the north bank of the river, and then south and southeast, still following the river, past a detector at MP 314.9, a detector at MP 314.6, Wilmor, a turn east, southeast, Edwards, and curvily east, still following the north bank of the river, past a detector at MP 311.5, the 8,350 ft. siding at Avon (MP 308.2), a detector at MP 305.1, a turn curvily southeast, Dowd, a detector at MP 303.8, and the 10,660 ft. siding at Minturn (MP 302.0, altitude 7,818 ft.), the operations and helper terminal for Tennessee Pass, where there are still a few yard tracks and the rump of a roundhouse.
Tennessee Pass provides the highest mainline summit in North America, and has a very extensive grade of 3% on the west (or north) side of the pass, with an altitude change of more than 4000 feet between Glenwood Springs, where mid-train helpers are often added, and the summit (almost 3000 feet from Minturn, where the last set of helpers is added), with the line running just east of due south along the east bank of the Eagle River, past Rex, a detector at MP 299.4, a detector at MP 298.0, a detector at MP 297.0, and the 408 ft. Rock Creek Tunnel (MP 296.8).
Now there are mines alongside the railroad tracks, which are split at Belden (MP 296.2) with the main on one side of the river and a 10,430 ft. siding on the other. The mines are (or were) accessed by precarious cableways that traverse the hillside from the old mining towns along the highway far above. The line passes the 396 ft. Belden Tunnel (MP 296.0) and a detector at MP 295.5, and turns east-northeast, along the north/east side of the river. Above the town of Red Cliff, a location for mineworkers homes (for the mines just to the west), US 24 crosses on a spectacular arch bridge, while the railroad continues to run alongside the Eagle River, far below. Beyond this location, the tracks follow the river, curvily just east of due south, while the highway disappears to the west.
There is a detector at MP 293.8, a bridge to the west side of the river, a detector at MP 293.0, a detector at MP 292.1, a bridge back to the east side of the river, a detector at MP 291.1, a bridge back to the west side of the river, and a detector at MP 290.2. The road and rails do not come back together until we reach the 8,260 ft. siding at Pando (MP 288.5, altitude 9,200 ft.), an area with large alpine meadows, where there was once a mountain-warfare training center (Camp Hale) during WWII (Bob Dole’s 10th Mountain Division trained here), where the line is running along the west side of a relatively-broad valley, past a detector at MP 286.7, the 242 ft. Pando Tunnel (MP 286.6) , and a detector at MP 285.6. The line runs along the cliffs on the west side of the Eagle River valley, while the highway is across the valley to the east, past Deen, a detector at MP 284,8, a detector at MP 283.6, and a detector at MP 282.9.
The Tennessee Pass line was originally narrow gauge; and in places the route of the narrow gauge line differed from the present standard gauge line, such as south of Deen, where the narrow gauge ran directly along the west bank of the river, while the standard gauge line runs along the foot of the cliffs, further west, with the two routes rejoining north of the Mitchell curves, named after a creek in the area, south of which the river turns away east, the route of the narrow gauge once turned away west to climb over the very top of the mountains on zig-zag curves, and the standard gauge line continues curvily south to the summit of the pass itself at 10,212 ft, where the single line enters the 2,550 ft. Tennessee Pass Tunnel (MP 281.2).
At the east end of the tunnel, the line bridges a small stream and reaches a flattish area (named Tennessee Pass, MP 280.3) where there are several tracks (including a 7,870 ft. siding and there was once a turntable for the helper locomotives (in steam days). This is where the helpers that have come up the west side of the pass are taken off their trains to return westward. Many trains climbing the west slope have both rear-end pushers and mid-train helpers, or two sets of mid-train helpers, to get their heavy loads over the pass.
Now at an altitude 9,560 feet, a drop of 600 feet from the summit, the line hugs the east wall of the valley, past Cranes Park, where the narrow gauge line rejoined the current route, a location where the standard gauge line once deviated to the west, a bridge over East Tennessee Creek, a bridge over a smaller creek, and a detector at MP 277.3, then crosses the highway and moves west across the valley to rejoin the original route, turning south again past Leadville Junction, where a line to Leadville once headed east, a bridge over the East Fork of the Arkansas River, a detector at MP 274.5, a former flat crossing with the erstwhile Leadville branch of the Colorado Midland, a detector at MP 272.6, the 7,800 ft. siding at Malta (MP 271.0), where the branch to Leadville used to depart the main on the east side, the erstwhile routing of the former Colorado Midland once came alongside to the west, and crosses the meadows where the incipient Arkansas River is now meandering gently, with glorious views of the many 14,000+ ft. snow-covered peaks lining the valley to the west (including Mount Elbrus, 14,433 ft and nearby Mount Massive).
The line turns just east of due south, bridging over the small river a couple of times, with the Colorado Midland's routing still to the west, past a detector at MP 268.7, a detector at MP 266.3, Snowden, where it bridges the river to run along its west side (and the Colorado Midland alignment crosses to the east side), a detector at MP 264.8, the 8,090 ft. siding at Kobe (MP 263.6), a detector at MP 260.0, a bridge to the east side of the river, Yale, a turn southeast past a detector at MP 257.2, and then curvily just east of due south again, bridging to the west side of the river past a detector at MP 254.9, the 7,640 ft. siding at Princeton (MP 252.1), a detector at MP 249.1, Riverside, and a detector at MP 247.1, and bridging back to the east side of the river past the 9,000 ft. siding at Americus (MP 244.7) and Wildhorse, then bridging back to the west side again, past a detector at MP 240.6.
The Colorado Midland alignment turns away, and a branch of the narrow gauge Denver, South Park & Pacific once appeared on the east side at Buena Vista (MP 240.3), and the main line bridges over the river again, past a detector at MP 239.7, Midway, a detector at MP 237.1, a bridge back to the west side of the river, the 6,890 ft. siding at Nathrop (MP 232.9), where the main line of the D, SP & P once crossed heading for Alpine Tunnel to the west, a detector at MP 230.0, and a bridge finally to the east side of the river, past a detector at MP 229.0, a detector at MP 228.5, a detector at MP 228.0, Swan, where it turns curvily just west of due south, following the river bank, a detector at MP 227.3, a detector at MP 226.5, a detector at MP 225.9, Arena, a detector at MP 224.7, a detector at MP 223.5, Hecla Junction, where a narrow gauge branch once headed east, and whitewater rapids on the river west of the line as it enters Brown Canyon.
Remnants of the old narrow gauge line (narrow formation and bridge abutments) can be seen at the north end of Brown Canyon, as the line heads southwest past the 9,960 ft. siding at Brown Cañon (MP 222.2), and turns south-southeast, away from the river, past a detector at MP 219.5, a detector at MP 218.5, and Belleview, rejoining the east side of the river before reaching the 7,240 ft. siding at Salida (MP 215.1), where the line turns southeast (to continue following the course of the Arkansas).
The original narrow gauge line of the Denver & Rio Grande had headed directly west from here, over Monarch Pass and through Gunnison to Montrose and thence to Grand Junction by the still extant branch. Much of this line remained narrow gauge until closure in the 1950s.