House's offer challenged each level's representative who was in favor of staying isolated. While most of the Vault dwellers wanted to refuse the offer, some residents were in favor of it. In 2274, Robert House contacted Vault 21's residents with an offer of inclusion in the resurrection of Vegas. Sarah describes it as 'pure New Vegas' as 'everyone has a chance and lady luck smiles if you play your odds right.' Chosen representatives gambled against each other in the main atrium and the winner earned the right to settle the dispute as wished by the collective. Everyone in the Vault was equal, it was created with a perfectly symmetrical layout, and all conflicts and problems were solved through gambling.
Located in downtown Las Vegas, Nevada, Vault 21 was one of the few Vaults that successfully protected its inhabitants while fulfilling the parameters of its experiment.