Under the California Streets and Highways Code, the entire Foothill Freeway is legally referred to as Route 210.

The freeway follows the foothills of these mountains, connecting the northeastern suburbs of Los Angeles with the Inland Empire.

Additionally, the I-210 designation has changed routings, previously including a portion of what is now the Orange Freeway (SR 57).

(b) Route 210 may be known and designated as the Southern California Native American Freeway or by the name described in subdivision (a) of Section 101.19.

After leaving Los Angeles, it enters northern Glendale and then La Cañada Flintridge where it meets with the Glendale Freeway and Angeles Crest Highway portions of SR 2 before turning due south towards the junction with SR 134) in Pasadena.

Portions of the Los Angeles County Metropolitan Transportation Authority's (Metro) light rail A Line runs in the median strip of I-210 from Pasadena to Arcadia, serving three stations at Lake, Allen, and Sierra Madre Villa.

The western segment consists of newer freeway, beginning at the east end of I-210 near San Dimas.

SR 210 extends eastward, eventually paralleling Highland Avenue, as it continues through Fontana.

It intersects I-15, an artery between Southern California and Nevada, about 10 miles (16 km) before it meets with I-215 in San Bernardino.

[13] The "curve" refers to the I-210 freeway as it turned south in an almost 90 degree angle in the city of Glendora.

The first section, starting at the eastern end of Foothill Boulevard in what is now La Cañada Flintridge, and going across the Arroyo Seco near Devil's Gate Dam to Canada Avenue in Pasadena, was opened in 1966; it was then signed as SR 118.

The section going northwest from Pasadena through La Canada Flintridge to the junction with I-5 in Sylmar was built in several stages between 1971 and 1977.

The first section to open was between Ocean View Boulevard and Lowell Avenue in La Crescenta, in July 1972, followed in November by the section between Berkshire Avenue and Ocean View in La Cañada Flintridge.

The last section in the San Fernando Valley to be completed was between Highway 118 in Lake View Terrace, and Lowell Avenue in La Crescenta.

In 1968, the Atchison, Topeka and Santa Fe Railway depot at Santa Anita, a historic structure built in 1890, was moved to the Los Angeles County Arboretum and Botanic Garden to make way for a section of the freeway passing through Arcadia.

In the 1990s, Caltrans began constructing extensions to the freeway from Glendora east to the former I-215/SR 30 interchange in San Bernardino.

Caltrans has petitioned the American Association of State Highway and Transportation Officials (AASHTO), the trade organization that oversees the designation and numbering of the Interstate Highway System, to resign the entire Foothill Freeway, including the entire segments of SR 210 and SR 30, as I-210.

The western freeway segment, planned since the 1970s and completed in 2002, replaced a western surface street segment that began with Base Line Road (sometimes spelled Baseline Road) at its intersection with Foothill Boulevard in La Verne and extended eastward into Upland.

Construction started on the eastern end from Foothill Boulevard (exit 47), and slowly moved east.

The final phase of the Foothill Freeway project involved the completion of the interchange with I-215 (exit 74).

[23] Caltrans District 8, in cooperation with the cities of Highland and San Bernardino and the San Manuel Band of Mission Indians, is currently evaluating ways to improve mobility and connectivity to the freeway at and near the Highland Avenue interchange, including a proposal to construct a new interchange to the east at Victoria Avenue.