The Sacramento Northern Railway (reporting mark SN) was a 183-mile (295 km) electric interurban railway that connected Chico in northern California with Oakland via the state capital, Sacramento. In its operation it ran directly on the streets of Oakland, Sacramento, Yuba City, Chico, and Woodland. This involved multiple car trains making sharp turns at street corners and obeying traffic signals. Once in open country, SN's passenger trains ran at fairly fast speeds. With its shorter route and lower fares, the SN provided strong competition to the Southern Pacific and Western Pacific Railroad for passenger business and freight business between Oakland and Sacramento. North of Sacramento, both passenger and freight business was less due to the small town agricultural nature of the region and competition from the paralleling Southern Pacific Railroad.

The SN had been two separate interurban companies connecting at Sacramento until 1925. The Oakland, Antioch, and Eastern Railway was a catenary wire powered line that ran from Oakland through a tunnel in the Oakland hills to Moraga, Walnut Creek, Concord, Pittsburg, to Sacramento. It was renamed the San Francisco–Sacramento Railroad briefly. The Northern Electric Railway was a third rail powered line that ran from Sacramento north through Marysville and Yuba City to Chico. It was renamed the Sacramento Northern Railroad in 1914. In 1928, the two lines combined to become the Sacramento Northern Railway under control of the Western Pacific Railroad which operated it as a separate entity. An extensive multiple-car passenger service operated from Oakland to Chico until 1941 including providing dining car service on some trains. Passenger traffic was heaviest from Sacramento to Oakland. Freight operation using electric locomotives continued into the 1960s.

The Vallejo and Northern Railroad was a proposed 58.15-mile (93.58 km) interurban railway line between Vallejo and Woodland, California. The company was incorporated on November 9, 1906, promoted by the same person who put forward the Dixon Branch. Terminal sites were purchased in Fairfield, Suisun, Vacaville, and Vallejo, California. Additionally, the railroad also began planning an extension from Woodland to Sacramento, going on to acquire franchise rights for running on Sacramento streets and purchasing property in Woodland. Despite the swift property acquisition, construction had not commenced, reportedly a result of the Panic of 1907. The company was merged into the Sacramento Northern Railway predecessor Northern Electric Railway in 1909 after Northern Electric floated $10 million ($350 million in 2024 adjusted for inflation) worth of bonds in Amsterdam. A single tram lettered Vallejo & Northern # 1 operated in downtown Sacramento from November 15, 1911 until 1914. Construction of what would become the Sacramento Northern Vaca Valley Line began in 1913; and line opened for service on May 16, 1914. Northern Electric combination cars numbered 103, 104, and 22 offered passenger service over this isolated branch until passenger service was abandoned in 1926. Motor #701 pulled carloads of freight transferred from barges and shallow-draft steamboats at Suisun. The line was connected to Sacramento Northern's main line via a new branch between Vacaville and Creed in 1930. Western Pacific Railroad proposed extending the Willotta branch of their Sacramento Northern subsidiary through Jamison Canyon to connect with the Petaluma and Santa Rosa Railroad (P&SR) as late as 1932, but the Great Depression and Northwestern Pacific Railroad purchase of the P&SR prevented such expansion. The connecting line through Cordero was relocated during construction of Travis Air Force Base in 1942, and diesel locomotives replaced electric operation in 1947.

The original, 93-mile (150 km) route connected Chico with Sacramento. The line began as the Chico Electric Railway (CERY), in operation beginning in 1905. The company had acquired two horse-powered street railways in Chico and Marysville, which were rebuilt for electrification. CERY was sold in 1906, after only a few months of operation, to the newly-formed Northern Electric Railway (NER). Northern Electric extended service to Oroville on April 25 of that year, continuing on through Marysville to Sacramento, beginning full service on September 1, 1907. A branch from Chico to Hamilton which crossed the Sacramento River via pontoon bridge was completed a few months later.

The company initially sought to expand. The Woodland Branch began service on July 4, 1912, with an intent to continue the line to the Bay Area. The Marysville and Colusa Branch started less than a year later, which was part of a planned expansion into the Sacramento Valley's west wide. At this time, the company additionally opened the isolated Willota–Suisun–Vacaville branch, intending it as part of the eventual route to connect at Woodland. As a stopgap, passengers in Sacramento could transfer to California Transportation Company riverboats in Sacramento to continue on to San Francisco. The NER went into bankruptcy in 1914, and was reorganized into a new corporation named the Sacramento Northern Railroad (SNRR).

The Southern Division began as the Oakland and Antioch Railway, which opened its line between Bay Point and Walnut Creek in 1910, extending to Lafayette the following year. While a bridge was planned to cross Suisun Bay, this never materialized; construction began around 1912 but ceased the following year. A wooden ferry, Bridget, was built to temporarily move trains between West Pittsburg and Chipps Island. This was done simultaneously to major expansion, with a new line run across the Sacramento Delta, trackage agreements with the Key System to their transbay ferry terminal in Oakland, and a new 3,500-foot (1,100 m) tunnel through the Oakland Hills. Regular service between Bay Point and San Francisco began on April 7, 1913. Bridget was destroyed by a fire in May 1914 — OAE rented tugs and barges until a new ferry was built. Her replacement, Ramon, was put into service by the end of the year. Full service between Oakland and Sacramento commenced on September 3, 1914. The Oakland, Antioch and Eastern Railway, as it had become known in 1912, entered receivership in 1920 and was reorganized as the San Francisco–Sacramento Railroad.

In 1925 the WP created a "new" Sacramento Northern Railway (SNRy), in order to group the growing collection of their interurban railroad holdings.^{[citation needed]} Thus, the Sacramento Northern Railway was created from two distinct interurban railroads. Western Pacific purchased the San Francisco–Sacramento Railroad in 1922 and proceeded to acquire the stock of the NER in 1927; they consolidated operations the following year. By retaining the Sacramento Northern Railway as a subsidiary rather than just absorbing it into the Western Pacific Railroad, the WP earned more income by interchanging freight with a separate Sacramento Northern Railroad due to extra fees earned from shipper-customers by interchanging freight from one railroad (itself) to another (the Sacramento Northern). Western Pacific also owned regional sister electric railroads, the Tidewater Southern Railway (TS) (Stockton to Modesto) and the Central California Traction Company (CCT) (Stockton to downtown Sacramento). The CCT used the same downtown Sacramento terminal and ran directly on Sacramento streets.

The two divisions used different voltages as well as different methods of current collection, thus only some powered equipment could traverse the entire Chico to Oakland route. When in Oakland, SN used Key System electric power. Some equipment carried a third rail shoe, a trolley pole, and a pantograph. The differing electrical systems, third rail for the North End and trolley wire for the South End, were retained. Cars from the higher-voltage southern division could operate over the whole line, but those in the northern division were relegated to that territory.^{[clarification needed]}