Laws and ballot initiatives for mandatory labeling have been proposed in more than 20 states.
While California's Proposition 37 failed in November, Whole Foods has decided to label genetically modified ingredients voluntarily.
On Tuesday, California voted down a referendum that would have required labels for genetically-modified foods.
Proponents of the bill say that if customers are made aware of the genetically modified contents of their foods, they will gravitate toward non-GMO options.
The USDA grants unrestricted use of GMO sugar beets, and California voters consider GMO labeling requirements.