From Palo Alto Wiki
Dennis Oliver was one of the Irish brothers-in-law (the other was D.C. McGlynn) who founded the city of Menlo Park. He was from Menlough on Lough Corrib, County Galway, Ireland.
He and McGlynn purchased 1,700 acres of the 35,250 acre Rancho de las Pulgas, the largest land grant on the Peninsula. They built two houses with a common entrance among the oak-dotted landscape and erected a tall wooden gate with three arches over the entrance. On the gate they inscribed the name "Menlo Park" in foot-high letters, and the date, 1854.
No one knows whether they abbreviated the name to "Menlo" (from "Menlough," their hometown) because the space on the arch precluded the longer version, because it was their way of Americanizing the name or because they just couldn't spell.