[5] Before the California Gold Rush, the Nisenan Maidu occupied both permanent villages and temporary summer shelters along the rivers and streams that miners sifted, sluiced, dredged and dammed to remove the gold.

[6] Explorer Jedediah Smith and a large party of American fur trappers crossed the Sacramento Valley in April 1827.

[6] Deprived of traditional foodstuffs, homesites and hunting grounds by the emigrants, the Nisenan were among the earliest California Indian tribes to disappear.

[6] During the 1850s, miners sluiced streams and rivers, including Secret Ravine, which runs through Rocklin.

The piles of dredger tailings are still obvious today, between Roseville and Loomis southeast of Interstate 80.

[7] Secret Ravine, at the area now at the intersection of Ruhkala Road and Pacific Street, was later mined for granite, some of which was used as the base course of the California Capitol Building; the earliest recorded use of the rock was for Fort Mason at San Francisco in 1855.

[8] In 1860, the U.S. Census counted 440 residents in the area of Secret Ravine, of whom about 16% had been born in Ireland and the majority of whom worked as miners.

[9] The area was referred to as Secret Ravine or the "granite quarries at the end of the tracks" as late as 1864.

[9] In 1864, the Central Pacific Railroad completed an extension of its track southwest from Newcastle to Secret Ravine.

It named the area Rocklin after its granite quarry and used the site as a refueling and water stop.

According to the 1870 census, Rocklin had grown to 542 residents,[11] and the majority of Irish immigrants had forgone mining and were working for the railroad.

[12] In 1869, a group of laid-off Chinese railroad workers moved to Secret Ravine to mine and raise vegetables which they sold locally.

[citation needed] Rocklin has a hot-summer Mediterranean climate (Köppen Csa), characterized by cool, wet winters and hot, dry summers.

The degree of diurnal temperature variation varies greatly depending on time of year.

[9] Top Rocklin employers include large multinational corporations, retail outlets, education and government.

A section of Granite Drive along Interstate 80 known as Toy Row has high-end auto dealerships, RV and Boat retailers, and a local antique mall.