Only 59 percent of high school students who started as freshmen in the 2006-2007 school year graduated four years later from District of Columbia schools, according to the data, which details state four-year high school graduation rates in the 2010-11 school year.
At the top of the list, meanwhile, Iowa stood alone, with an 88 percent graduation rate.
Wisconsin, the home state of GOP vice presidential candidate Paul Ryan, tied for second-best with Vermont, posting a graduation rate of 87 percent.
Other selected state rates:
North Dakota—86 percent
New Hampshire—86 percent
New Mexico—63 percent
The 2010-11 graduation rates are preliminary, state-reported data, according to the federal government and the Education Department says it will release final rates in the coming months. Education Secretary Arne Duncan said this is the first year for which all states used a common measure.