Los Angeles

2008 Population: 35,000

2012 Projected Population: 49,756

Notable Investment: $1.4 billion in light rail projects

More than half of L.A.'s downtown population is single and works within the area. Development projects like entertainment-focused L.A. Live and the mixed-use Grand Avenue project are expected to have a $10 billion economic impact on downtown. Fifteen subdistricts within L.A. give the city a diverse vibe.

Challenges: Real estate prices have softened in its condo and loft markets.

Sources: DowntownL.A.com, Central City Association and Downtown Center Business Improvement District