Final answer:
The information provided does not name the group boycotting the Turnpike, but details the Montgomery Bus Boycott, a pivotal event in the civil rights movement led by African Americans against segregated buses.
Step-by-step explanation:
The group that tried to boycott the Turnpike when it first opened, citing high toll rates, is not explicitly named in the information provided. However, within the context of civil rights actions during the mid-20th century, African Americans engaged in several boycotts, the most notable being the Montgomery Bus Boycott. This boycott was a response to segregated bus seating and other systemic injustices, not specifically high toll rates on a turnpike. In this case, 50,000 African Americans in Montgomery united to avoid city buses for 381 days, crippling the financial stability of the bus system. This successful protest was a pivotal moment in the civil rights movement, demonstrating the power of collective grassroots actions against racial injustice and leading to the desegregation of the city's buses.