This infographic is from 2011 stating 1% vegan.
According to Wikipedia, it could be 6% or 7% in 2013. Or it could be .5% in 2008. Another interesting fact, Mike Tyson is vegan and Da Vinci was…
Vegetarianism was endorsed in the United States in 1838 by the American Health Convention. In 1971, 1 percent of U.S. citizens described themselves as vegetarians. A 2013 Public Policy Polling survey found 13% of Americans identify as vegetarian (6%) or vegan (7%). A 2012 Gallup poll found 5% of Americans identify as vegetarian and 2% as vegan. A 2008 Harris Interactive poll found that 10% of adults “largely follow a vegetarian-inclined diet,” with 3.2% following a vegetarian diet and 0.5% identifying as vegans. A 2000 Zogby Poll found that 2.5% of respondents reported not eating meat, poultry, or fish; while 4.5 percent reported not eating meat.