Two of the most important symbols in "The Outcasts of Poker Flat" are the town of Poker Flat itself and the group of "objectionable characters" that it sends out into the wilderness. These two groups are symbols of the New West against the Old West.
For example, Harte tell us that "Poker Flat was 'after somebody'" because "it had lately suffered the loss of several thousand dollars, two valuable horses, and a prominent citizen." Harte's story is set at a time when California mining towns were beginning to evolve from rough, uncivilized collections of people to towns in which the inhabitants wanted order, law, acceptable social behavior--in other words, some form of a civilized society. Poker Flat has reached a point at which the Old West, represented by lawlessness and immoral behavior, is no longer to be tolerated, and so the town casts out those who do not fit properly into a new form of civilization.
The group of outcasts--a prostitute, a drunkard, an anti-social old woman, and a gambler--represent the Old West, the rootless people who do not contribute to the betterment of the town as a whole. They become, in essence, the victims of a developing society in which they have no proper place, and they represent the West that no longer exists. The conflict between the two types of society is resolved by the town simply getting rid of those who do not fit the mold of New West citizens.
Another important symbol is a combination of the landscape and weather in which the story takes place--nature. As we know, the outcasts are forced to leave Poker Flat in November, a time in the Sierra Nevada when people need to be established in a place where they can survive a very harsh winter, which can start as early as November and immobilize everyone until spring. As we find out, the meager provisions provided by Tim Simson, the "Innocent," and Piney Woods are not sufficient to overcome the onslaught of nature.
The outcasts themselves become symbols of positive behavior. Based on the initial description of this group--all of whom have serious personal flaws--we do not expect the turn in their behavior. Except for the drunkard, each character eventually exhibits empathy, compassion, and, in the case of Mother Shipton, complete self-sacrifice when she saves an entire week's rations for the two youngsters:
It contained Mother Shipton's rations for the last week, untouched. "Give 'em to the child," she said, pointing to the sleeping Piney.
In essence, Mother Shipton, despite her flawed character, hastens her own death by trying to insure that "the child" (Piney) survives just a bit longer. We see the same compassion on the part of The Duchess, and when Oakhurst realizes the group is doomed, his last effort on its behalf is to stack as much firewood as he can find near the cabin in order to prolong the group's survival even as he walks away to commit suicide (to keep from freezing to death). These flawed characters, then, become symbols of humanity at its best--compassionate, empathetic behavior in the face of certain death.
One question Harte poses in this story is this: Who, in the end, is the most civilized? The town of Poker Flats? The group of seriously flawed characters?