I would suggest that some formative events took place before the action described in The Help.
The death of Aibilene's son Treelore happened some years prior to the opening of the story, but that event greatly impacted Aibilene, her future employment situations, and her eventual cooperation with Skeeter in recording the stories of the black women working for white women in Jackson.
The unexplained departure of Constantine from employment with Skeeter's family, while she was away at college, turns out to be another important event. When Skeeter's mother is forced to admit the full circumstances of Constantine's behavior and the reasons she left, Skeeter's outrage toward the prejudices of the people around her intensifies, supported by a very personal sense of regret.
Yule May's imprisonment is important because it is the event that convinces many of the other black women that their stories need to be told, that it is worth the very considerable risk involved to meet with Skeeter and have their comments added to the book's contents.
A series of connected incidents - Miss Hilly's campaign to pass the law requiring separate toilets for the black help, Skeeter's article suggesting that toilets be left on Hilly Leefolt's front yard, Hilly's vow to get revenge on Skeeter - constitutes a major escalation in the war of wits between Skeeter and the engrained prejudices and practices of the whites of Jackson.
The events that take place in Jackson are echoed in the background by the Civil Rights Movement that was escalating in level of activity and commitment of persons involved during the time period covered by The Help. Martin Luther King leads the March on Washington, Medgar Evers is assassinated, President Kennedy is assassinated - events that increased the level of risk and the level of commitment to the importance of getting Skeeter's book published.