The first section of the Golden State Freeway (eventual I-5) to be constructed & opened was between Riverside Drive near the L.A. Zoo in Griffith Park and Alameda Ave. in Burbank; that was opened in early 1957. By the end of that year it had been extended south to between Glendale Blvd. and Los Feliz Blvd, using temporary ramps to empty out onto Riverside Drive. Included in that segment was the Colorado Blvd. extension (part of LRN 161/SSR 134). By mid-1958 US 99/6 had been rerouted onto the freeway using the Colorado extension (an arrangement that lasted for about 3 years). Northbound, US 99/6 remained on San Fernando Road (the original alignment) to the Colorado extension, then used that extension to the freeway mainline. It went north on the freeway to Alameda, where it turned west with SSR 134 to Victory Blvd. At Victory Blvd. the temporary routing turned north, using that street to the "Five Point" intersection of Victory Blvd., Burbank Blvd., and Victory Place. While Victory Blvd. turned due west at that intersection, the 99/6 temporary routing continued north on Victory Place, which merged with the original San Fernando Road alignment east of Lockheed (now Hollywood/Burbank) airport. This rerouting was necessary because northward construction on the Golden State Freeway used the alignment of Front Street, the former route, in central Burbank; the street was demolished in late 1957 to make room for the freeway, which was opened to traffic as far north as Burbank Blvd. in the spring of 1959.
The segment along Riverside Drive, which included the SSR 2/Glendale Freeway interchange, was opened to traffic in the spring of 1961; southbound, it emptied all US 99/6 traffic onto the southbound Pasadena Freeway over the present ramp system bordering Elysian Park. The first Golden State Freeway section to actually receive I-5 signage, between Broadway on the north and Boyle St. on the south (near Hollenbeck Lake, just north of Wilshire Blvd., and including the San Bernardino Freeway interchange), had opened in early 1960, with the I-5 ramps to the southbound Santa Ana Freeway (US 101) opening a year later. The final section, between Broadway and just north of the Pasadena Freeway (including the interchange with that freeway, then US 66, and the L.A. river bridge) opened in late 1962.
North of Burbank, the segment between Burbank Blvd. and Lankershim Blvd. in Sun Valley opened in the spring of 1961, extending north to Van Nuys Blvd. in early 1963 (this section included the inital ramps to the planned Hollywood Freeway -- originally intended to be part of US 6, but, after the '64 renumbering, becoming CA 170). The final I-5 segment between Van Nuys Blvd. and the existing Golden State Freeway alignment north of Sylmar was opened to traffic in the fall of 1963, essentially finishing the freeway from its inception at the E.L.A. interchange to the point where it departed the San Fernando Valley.
As a born & raised Glendale kid, I had front-row seating for the unfolding of this freeway -- I remember badgering my dad to drive me over the temporary Victory Blvd. alignment so I could see how it was signed (and as long as we were out that far in Burbank, to take me to Albin's Hobbies so I could see the new Lionel locomotives for '58 Xmas!). If it was anything that rolled along the ground, it interested me as a youngster (some things never change!).