The last beefy paragraph of Ragtime details the lives of many of the characters after the era of ragtime had ended. It's a long passage—go read it—but we'll tackle the issues it raises here.
First, we get our happy ending: Mother and Tateh get married, each changing with the times, adapting and learning and progressing towards the future. Tateh embraces filmmaking and makes a wonderful living, and at the end of the book he has a vision of a series of films, which will be the "Our Gang" series, about children of all races and types living and playing together. The happy endings in this world, the novel suggests, belong to those who embrace ambition and multiculturalism.
We know that Emma Goldman gets deported, suggesting that history might not be too keen on people that are in such out-and-out defiance of society. Poor Emma. She was ahead of her time with the whole "no corsets" thing.
Evelyn Nesbit falls into obscurity once she's lost her cherub-girl prettiness. Here's a neat little lesson about planning for the future (it's right around the corner) and not relying on looks alone.
The last sentence shows us that we've won the war, but a crazy murderer (Harry K. Thaw) marches annually in the Armistice Day parade. Life goes on, continually full of lunatics and parades and surprises.