They're the largest generation in our nation's history, accounting for nearly a quarter of the U.S. population, and they're following the sunset.

Millennials, those between the ages of 18 and 27, are expected to have the biggest impact on western markets, according to a recent report from demographic research firm Nielsen. The report, dubbed "Millennials: Breaking the Myths," found that nine of the top 10 markets for Millennial concentration are found west of the Mississippi: Surprisingly, Washington, D.C. is the only east coast city on this list.

The numbers below are based on the Millennial percentage of a market's population, and cross-referenced by an index of Millennial concentration.

1.    Austin, TX (16%, 120)

2.    Salt Lake City, UT (15%, 117)

3.    San Diego, CA (15%, 117)

4.    Los Angeles, CA (14%, 109)

5.    Denver, CO (14%, 109)

6.    Washington, DC (14%, 109)

7.     Houston,  TX (14%, 108)

8.    Las Vegas, NV (14%, 108)

9.    San Francisco, CA (14%, 107)

10. Dallas-Ft. Worth, TX (14%, 106)

-Linsey Isaacs is an assistant editor with Multifamily Executive magazine. Follow her on twitter @LinseyI  to continue this conversation.