There’s a handful of roles made for a single actor. It’s rare that an audience will remember an actor by a single role. It takes a confluence of happenstance–timing being the big one. The right actor in the right circumstance with the right personality and experience meets the right writer who writes for the right projection of self; the plot is timely and impactful and the characterization is meaningful, riddled with emotional cues and the director and supporting cast have the right combination of empathy to allow the role to breathe or constrict, as written.
This is rare. It’s rare to get a handful of these circumstances in the same state, and even more unlikely to have them convalesce on the same set. George C. Scott as General Patton in Patton is one. Daniel Day-Lewis bucks this trend and seemingly rearranges spacetime to force the pieces together as Christy Brown in My Left Foot, William Cutting in Gangs of New York, Daniel Plainview in There Will Be Blood, President Lincoln in Lincoln, and about half a dozen others. One more to add to this list is Gregory Peck as Atticus Finch in To Kill a Mockingbird.
We’ve got to consider context, too. The external factors that audiences have access to were off the radar to audiences in 1962: it was an age of simmering indifference and false innocence. Americans were lulled into great times of growth. Post-war America ushered in a generation of prosperity and security, mildly plagued by simmering tensions in the East. Fathers and brothers who served their country and came home in Europe or Asia were rewarded with access to education, credit and stable jobs. It was never this way for black Americans, though. It wasn’t even a secret.
Harper Lee wrote To Kill a Mockingbird from within an era of piercing failure of justice. Her words, with the benefit of experience, said the quiet part deceptively loud. Through her characters, tightly constructed, the reader sought idealism and the aforementioned justice for humanity. She defended different and championed compassion for the men and women she made. What American idealism had done for 300 years–dehumanized the black experience–Harper Lee, herself white, tried to tackle over 200 or so pages. For whatever looming threat lurked overseas unbeknownst for generations, the internal war we’d been fighting in America raged, nearly invisible to the naked eye. We’d fought to free the slaves a hundred years ago, but the lives of others remained nominally unaffected. Never forget Emmett Till.
Lee’s book, and Robert Mulligan’s movie, is what gives those who would otherwise ignore civil rights of others standing to fight for them, for all Americans, and especially black Americans.