Gallup surveyed U.S. adults in the 50 states and the District of Columbia to determine how many self-identify as gay, lesbian, bisexual, or transgender. The GLBT percentage was highest in D.C. (10%) and lowest in North Dakota (1.7%). All the states were within 2 percentage points of the nationwide average of 3.5%. The states with proportionally larger LGBT populations generally have supportive LGBT legal climates. With the exception of South Dakota, all of the states that have LGBT populations of at least 4% have laws that prohibit discrimination based on sexual orientation and gender identity and allow same-sex couples to marry, enter into a civil union, or register as domestic partners. Of the 10 states with the lowest percentage of LGBT adults, only Iowa has such laws.