Originally only those with primarily British heritage were given full acceptance into American society and others, most notably Native and African Americans, were excluded from rights that were extended to white people. Over time, other lighter skinned people (e.g. Germans, Irish, Italians, etc.) were accepted as they downplayed their own ethnicity and adapted to the British-inspired values and customs that dominated the mainstream way of life within the United States.
As Rodriguez notes, as more and more immigrants came to the U.S., whiteness became more defined by who wasn't black rather than who was "white." He has this to say:
"Many books and articles have been devoted to explaining what it means to be white in America, but my favorite way to get at it is to describe an interview I helped conduct three years ago with a retired sheriff in Sunflower County in the Mississippi Delta, where, like most places in the U.S., the "white" population is actually a fragile amalgam of diverse subgroups.You can read the complete article here. Thanks to Racialicious for the link.
"Are Lebanese white people?" we asked the 71-year-old gentleman who considered himself white. "Yes," he said, "although they're real dark." How about Italian Catholics; are they white? Sure. And Jews? Yes. What about the Chinese? "Yes," he said, "they go to the white schools." And Mexicans? "They're becoming more white," he said. "More of them are getting an education."
Then what is a white person? we asked. After some confusion, our interviewee gave us this answer: anybody "who isn't black."
Over the decades, new immigrants to these shores were obliged to fit themselves into this black/white racial scheme. Not surprisingly, most chose to identify themselves with the group that had full rights. In books such as "How the Irish Became White," scholars have traced the path that immigrant subgroups took to become considered part of the "white" race. It's a poignant and peculiarly American journey. The protection and status of whiteness was not without costs. Most distinct subgroups gradually lost their distinctiveness. Their members traded specific ethnic labels -- Italian, Swedish, French -- for the generic racial label of "white." They exchanged identities that told us something about their unique histories for an elastic racial category that mostly tells us what they are not."