From 1910 up to some point in the 1980s there were twoclass one railroads that served customers on R.
Way back in 1865, the principals of the Central Pacificbought out the pioneer Sacramento Valley Railroad . The SVRR was completed in 1856 and ran down R street on its way to Folsom. The Central Pacific was leased to and generally became known as the Southern Pacific in the 1880s. For a time SP's R Street line was part of the Placerville Branch. Within my 'focus' area of R Street (from Front to 21st Streets) the SP served the businesses mostly on the southern side of the street.
The second class 1 railroad, the Western Pacific, arrived in 1909. The WP had significant terminal facilities on the western most part of the street including freight houses, packing sheds leased to produce shippers, a scale house, and a team track area with an overhead 20-ton capacity gantry crane. East of 7th Street, the WP shifted its line a little north and continued east down the Q-R alley (also known as Whitney Alley) until the line wyed out to the WP north-south mainline between 19th and 20th Streets. From the alley, the WP served a number of industries facing the north side of R Street from their 'back doors'.
Both railroads interchanged traffic with each other on a couple of transfer tracks on R Street between 4th and 7th Streets.
Also making an appearance on R was the Sacramento Northern. This WP owned electric interurban was 'under wire' until the mid 1950s and they used WP track up to 3rd Street to service the big Del Monte plant on Front Street. After the wires came down the SN used the WP R Street/ Whitney alley line to get from one part of Sacramento to another but they did not have any customers of their own on R.
Eventually the Union Pacific bought out both the WP (1983) and SP (1996) railroads, and rail services were mostly gone from my R Street study area by the late 1980s or so. Only the Sacramento Bee at 21st and R still remains a rail customer (and from what I hear, rail delivery of newsprint rolls is becoming more and more infrequent).