The indigenous inhabitants of Altadena, and Pasadena, were the Hahamog-na, a Tongva Native American tribe who lived in the Arroyo Seco. Hahamogna, the Chief, was met by General Portola of the Mexican Army in 1770 as he was making an exploratory expedition of Alta California. With the establishment of the San Gabriel Mission (1773) and the City of Los Angeles (1781), the south lands of California were properties claimed in the name of the King of Spain.
Altadena is the northernmost portion of Rancho San Pascual as established by the Mexican Government in 1826 after they had claimed independence from Spain. California was annexed in the Treaty of Guadalupe Hidalgo in 1848 and became a state in 1850. The Mexican Ranchos were then open to settlement from other parts of the Country. Rancho San Pascual was settled by the Indiana Colony in 1874 and incorporated as Pasadena, a Chippewa name derived from a translation for “Crown of the Valley”, in 1886. The highland areas, such as Altadena, remained undeveloped areas of the Los Angeles County.
Altadena is presently famous for it beautiful Christmas Tree Lane during the holdays.