Answer:
The first person in American was probably a Native American who crossed the land bridge.
Positive--resulted in the lowering of the voting age to 18, contributed to the end of the Vietnam War, contributed to furthering the civil rights movements of the time.
Negative--they were violent and led to the deaths of many in riots and shootings, their means were not taken seriously by adults and conservatives of the time,
I believe the answer you are looking for is the homestead act of 1862
