How has the American agriculture changed during this last century?

How has American culture's notion of "race" changed in the last century or two?

• Many historians and anthropologists have observed that "race" is a social construct, a way of mentally organizing the many different types of humans into buckets, and does not seem to really correspond to any relevant biological differences.  In American culture in 2014, most Americans would probably say there are several major racial categories: black, white, Asian -- and then it becomes a little less clear how people conceive of South Asians, Latinos, people from the Middle East --- people disagree somewhat on whether these are racial groups, ethnic groups or something else.  For example, a Persian-Iranian-American friend of mine explained that Americans are sometimes unsure whether they view Persians as "white" or "Middle Eastern" or even "Asian." And even these categories were not necessarily in place in people's minds until recently.  For example, in the late 1800s, some Americans felt that Irish and Italians were not "white" although everybody today would call these people white. In general, how has the current view of "race" developed?

• Answer:

  The distinctive US feature starting with the Jim Crow era is the one-drop rule lumping mulatto and other mixed-race castes with blacks. In many New World societies they had been a category of their own, including in Louisiana and I think even Charleston. "White" has always been ambiguous with respect to groups not yet established in large numbers. In the slavery era, the main concern (besides Indians) was slaves and those related to slaves, vs. other free population, leaving the latter sharing legal status with whites. The US Census has always counted Middle Easterners as white, counted Mexicans as white because of their equality under the Treaty of Guadalupe Hidalgo except for the 1930 census until the recent shift to self-reporting of race, and was ambiguous on South Asians until categorizing them as Asians largely on their West Coast economic role similar to East Asians.