Boulder, Colorado has a long history of prioritizing alternative transportation and limiting sprawl through policies protecting open spaces. In the 1950s-60s, Boulder grew rapidly due to new federal labs and university expansion. To control growth, citizens voted to restrict development and purchase open lands. Today, Boulder residents bike and walk much more than average and have shorter commutes due to extensive paths and transit. However, high housing costs now threaten diversity as many workers cannot afford to live in Boulder.