Manuel Valenca was born in Marin County on Rancho San Jose in 1856, six years after California became a state. He was tied to the aristocracy, his family having received many land grants in the San Francisco area. He is a descendant of General Gabriel Valencia, the first governor of Sonora under Spanish rule. His grandfather came to Alta California and was an administrator at the Presidio in San Francisco.
Manuel studied with Jules Tavernier and also at Santa Clara University. He spent some time in Mexico and was a member of the Esquela de Bellas Artes de Mexico.
Manuel worked as a commercial artist and was an art editor of the San Francisco Chronicle. His position at the Chronicle was paid for by art patron, M. H. de Young. After the '06 Quake, he moved his family to San Jose but continued to commute to the city. He also was an illustrator for the "War Cry," the Salvation Army newspaper.