Born to a Communist couple living in Madrid, the toddler Dolores boards the last train out of town as Madrid is about to fall to the Nationalists in 1939. They get to Valencia and then board a ship to Cuba.
Growing up in Cuba, Dolores becomes active in the Communist Party and joins the 26th of July Movement headed by Fidel Castro. But after he comes to power, she soon sours on his repressive regime and joins the resistance. When Castro's secret police crush the resistance after the bay of Pigs invasion, Dolores flees to the US. Then she makes her way to Maine, hoping to get far enough away from Cuba that Castro's agents won't find her.
Dolores Claiborne wound up in Maine because...well...Stephen King.