Final answer:
Open Racial Triangulation during the period of 1850-1950 challenges traditional notions about black history and civil rights activism, revealing the complexity of the era.
Step-by-step explanation:
The significance of Open Racial Triangulation during the period of 1850-1950 is that it challenges the traditional understanding of black history being limited to the South, as well as the idea that civil rights activism was exclusive to the 1950s and 1960s. Historians are now focusing on local history to reveal the complexity of the era, which saw a rise in black education and entrepreneurial ventures alongside racial violence.