The California portion of US 50 runs east from Interstate 80 (I-80) in West Sacramento to the Nevada state line in South Lake Tahoe.

The remainder of the highway, which climbs along and out of the canyon, then over the Sierra Nevada at Echo Summit and into the Lake Tahoe Basin, is primarily a two-lane road.

[5] At the US 50/Business 80/SR 99 interchange, Business 80 splits to the north, SR 99 heads south, and US 50 continues east as the El Dorado Freeway[6] and the Lincoln Highway.

In 1968, it was the site of the U.S. Olympic trials for men's track and field, held at a temporary facility in the parking lot of the Nebelhorn ski area.

Along the Humboldt River in Nevada, the Mormons met Joseph B. Chiles, who was leading a westward wagon train to California, and told him of their new trail.

[20] John Calhoun Johnson of Placerville surveyed and cleared a shorter, lower (and thus less snow-covered) trail east from that town in 1852, completing the work by the summer.

Returning to the river between Kyburz and Strawberry, he then continued alongside it to the crest at Johnson Pass, where a steep slope descended to Lake Tahoe.

Two years later, the counties of Yolo, Sacramento, and El Dorado, all of which would be benefited by further improvements, began planning and carrying out work.

The first toll-supported bypass of Peavine Ridge was built by Oglesby and opened in 1861, leaving the old road from Placerville at Pollock Pines, following the ridgetops and slopes south of the South Fork American River, crossing the river east of White Hall, and then following US 50 along the north bank to the 1858 county road west of Kyburz.

Toll collection ended in California in 1886, when El Dorado County bought the privately improved sections and made them public roads.

[22][29] The Pony Express used this route from its beginning in April 1860 until July 1, when its western terminus became Folsom on the Sacramento Valley Railroad.

The Department of Engineering took over its maintenance in 1907, immediately completed a survey and posted granite milestones that marked the distance from Placerville, and in 1910 started sprinkling the dirt road with water in summer to keep down dust (as had been done in the 1860s).

A 1915 law added the short distance from Smith Flat west to the east limits of Placerville to the state road.

[25][35][36][37][38] With the passage of the first state highway bond issue in 1910, the Department of Engineering was directed to lay out and construct a system connecting all county seats.

[39] Between El Dorado and Placerville, the state had two routes to choose from, including one via Diamond Springs (present SR 49), where it decided improving a cut would be too expensive.

[40] In 1917 the mileage that had been added by special laws, rather than as part of bond issues, was consolidated with the rest of the system, and Route 11 was extended east to the state line.

Contrary to the Lincoln Highway Association's policy of marking the most direct route, this deviation was explained simply as "for those tourists desiring to see Lake Tahoe".

[48] As part of the state project to pave this portion, the old road was bypassed in several areas, completing the final two-lane alignment.

A bypass (now Mother Lode Drive) around El Dorado and the winding Forni Road was completed in 1938, and the improvement was extended west to Shingle Springs in 1947.

A short relocation north of White Rock, between Bidwell Street and Bass Lake Road, opened in 1940, and was extended west beyond Hazel Avenue, bypassing Folsom, in 1949.

[68][69] For many years, the four lanes from Sacramento stopped at Riverton, where the original two-lane road continued through the canyon and over Echo Summit.

[70][71] The state rejected a proposed $133 million total realignment between Riverton and Kyburz in 1985, instead opting for a less expensive program of spot improvements including new bridges and passing lanes.

A project to make more permanent repairs and prevent future closures began on July 31, and from September 2 to October 24 the highway was closed during the week to allow for more efficient reconstruction.

The state signed the detour, which followed Sly Park Road, Mormon Emigrant Trail (the old ridgetop Carson Route), SR 88, and SR 89 (over Luther Pass), as Alternate U.S. Route 50,[75] a designation not approved by the American Association of State Highway and Transportation Officials, which generally assigns new bannered U.S.

[77] Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, based on the alignment that existed at the time, and do not necessarily reflect current mileage.