For decades now, US History survey classes have been divided by the Civil War wi

For decades now, US History survey classes have been divided by the Civil War with the first half covering up to 1865 and the second half covering 1865 to the present.  Discuss why you think historians settled upon this demarcation and why it persists to this day.  What are some other turning points in American history that historians have emphasized or should emphasize?  How might these other turning points influence where new American history surveys begin and end?