The human inhabitants were among the most peaceful beings in the galaxy, and to preserve their beautiful planet, had their cities built atop sandstone bluffs and on large stilts in the seas.
Alderaan further represented itself as a peaceful culture just after the Clone Wars, when all weapons were outlawed and put on a ship which was forever making random hyperspace jumps throughout the galaxy.

At the age of seventeen, an Alderaanian became an adult, and it was customary that the adults in Alderaanian society didn't cut their hair.

In the late days of the Republic, Alderaan was represented by the politicians Bail Organa and Bail Antilles, and during the time of the Empire, Princess Leia Organa was the senate representative.
While Palpatine was in power, the Organa family began a resistance to his Presidency, and Alderaan was one of the first supporters for the Alliance to Restore the Republic.

While being the representative of the Senate, Leia Organa was captured aboard the Tantive IV over Tatooine while intercepting vital Imperial plans. Leia was then taken to Grand Moff Tarkin for questioning about the Rebel hidden fortress, and he threatened to destroy Alderaan if she didn't comply with his request.
When Leia lied about the location of the Alliance base in order to save her planet, Tarkin ordered Alderaan to be fired upon. With one blast, the entire planet was destroyed. Alderaan is a prime example of the damage that the Empire could achieve.

Had it not been destroyed, Alderaan would probably have stayed a leader throughout the Rebellion, and even in the fight against the invasion of the Yuuzhan Vong.