http://www.21-grams.com/content/prodnotesData.php

"Given the movie's Middle American setting, Memphis provided the necessary diversity of people and locale to color every frame of 21 Grams. Iñárritu found it to be 'unique, and quite different from all the cities in the United States that I've known and visited. It reminds me a little bit of a Latin American city. Memphis has a strong personality and the people there still have their feet on the ground. It's the heart of America, with a nostalgic sad feeling.'"