Starting Oct. 1, millions of Americans will be able to sign up for health care coverage through state or federal marketplaces, known as "exchanges," for coverage that would start Jan. 1 2014.

A central part of the Affordable Care Act, exchanges will allow people to compare plans online and learn whether they are eligible to get discounted coverage. 

Supporters of the exchanges say they will give greater choice to consumers and bring costs down.  

The ACA will also expand Medicaid, the federal health program for the poor and disabled that is administered by the states, if the state has opted for the expansion. As of Sept. 24, only 26 states have committed to the expansion, which begins in January. In those states, the program will be extended to include any individual whose income falls below $15,000, or $29,700 for a family of four.   

The first map shows the types of health care exchanges being set up in each state. The second map shows Medicaid expansion by state and the number of uninsured individuals in each who would be newly eligible for coverage under the ACA.

Source: The Commonwealth Fund

Sources: The Urban Institute and Georgetown University Center on Children and Families