Graham Hill Road was built to connect Isaac Graham’s sawmill near Zayante with Santa Cruz in the mid-1800s, and has been referred to as “the first highway in the west.”1 Depending on who you asked, Graham might be called “asesino y valiente” (assassin and bully), or “a bummer, a blow hard, and a notorious liar without an atom of honesty in his composition,” or “a stout, sturdy backwoodsman of a stamp which exists only on the frontiers of the American states.”2
He built the first steam-powered sawmill west of the Mississippi River. He also created the first whiskey distillery in the American west, which was so popular it became known as a “wild and roaring camp.” Roaring Camp Railroads can still be found near the other end of Graham Hill Road.
But perhaps his most significant contributions to the State of California came in the late 1830s and early 1840s. He and about two dozen other “riflemen” were hired in 1836 by ambitious, young Juan Bautista Alvarado, to help in a coup d’etat in Monterey (then capital of Alta California) to overthrow governor Nicolas Gutierrez. After Alvarado became the new governor, apparently he didn’t compensate his mercenaries well enough and they became restless. Fearing that his own position of power might be in jeopardy, Alvarado had Graham arrested in 1840 and tried for treason. He and 40+ other Englishmen and Americans were imprisoned in Mexico for a year. This significant international incident became known as the Graham Affair, and it helped encourage the young United States to acquire the Alta California territory that Mexico seemed to be only weakly protecting.
So thanks, Isaac, we guess 
!
BTW If you want to pay your respects, his Last Known Address is in Evergreen Cemetery at about N 36° 58.877 W 122° 02.097.
1 Obituary for Graham from the Pescadero Daily Alta, November 1863
2 Dorothy Allen Hertzog, in her thesis on Isaac Graham: California Pioneer (Santa Cruz Main Library — microform), quoting from various sources