The conclusion of Dr. King's letter can be thought to be comprised of the final three paragraphs. When he begins the conclusion, King begins the third-to-last paragraph with the words "Never before have I written so long a letter." By referring specifically to the letter itself, King is marking a transition from the content of his argument to his final thoughts and words. At this point the letter departs from King making claims of fact, value, and policy, and his tone shifts from that of a crusading activist to a man speaking directly to his audience about what his intention has been in crafting the argument.
The introduction of the letter can be thought to be comprised of the first twelve paragraphs. In them, King first explains why he is writing the letter, and why he is in Birmingham in the first place. He is answering a letter signed by local clergyman who claim that King's demonstrations are "unwise and untimely" and imply that he is an outside agitator who needs to leave and let the area officials resolve the issues at hand. King rebuts the idea that he is an outsider, because he believes that it is his job to address social injustice wherever it occurs. He outlines, in these opening paragraphs, what he and his followers are attempting to accomplish and their reasons and methods for doing so. The introduction is an assurance that he is not in Birmingham to create trouble or incite violence.
The rest of the body paragraphs constitute the "middle" of King's letter. In it, he lays out a reasoned argument with appeals to ethos, logos and pathos, using rhetorical techniques including anecdote, analogy, firsthand and secondhand evidence as well as concession and refutation, to build his argument that the civil rights of African Americans must be fully and freely granted in the country.