Where am I and what is this????

I've just passed this monument. It was made famous in a movie about aliens. A better clue lies in the Indian myth about how this strange formation came to be...here goes:

7 girls were playing happily, when suddenly, a giant bear came bounding out of the woods. The bear began to chase the girls. The girls ran as fast as they could, but the bear was getting closer and closer... They 7 girls saw a flat rock and quickly climbed up on it. They realized the bear would still be able to reach them and so began to pray to Wakan Tanka for help. Because their hearts were so pure, their prayers were answered. The rock began to grow and rise up into the air. The angry bear, scratched and clawed at the rock trying to reach the girls, but to no avail. The rock continued to grow until it became a tower that reached a heavenly height. Then, the 7 girls, being of pure heart, were transformed into 7 bright stars, which together form the big dipper.

If you're stumped....here is another clue. Just over the boarder from this formation lies a town also made famous by Hollywood. But, before Hollywood a man with a reputation as a gun fighter, lawman, stagecoach driver and generally a fearsome dude made his home here. He was shot and killed while playing poker in this town, allegedly holding what became known as the "dead mans hand"...a pair of aces and eights. He lies buried in the town cemetery, next to Calamity Jane. Who is he, and where is the town?