Maryland has become the first state in the nation to make plans to count prisoners at their last known home addresses, not their prison addresses, for purposes of redrawing federal, state and local legislative districts.

Traditionally, when legislative and congressional districts are redrawn using census data, prisoners are included where they are incarcerated. But some state officials say that gives outsize power to rural areas where many prisons are located, at the expense of urban areas that often are prisoners’ homes.

The Census Bureau announced in February that it would release detailed numbers earlier than usual to give more power to states to use 2010 Census data to exclude prisoners from being counted at their prison locations for redistricting purposes. On Tuesday, Maryland Gov. Martin O’Malley (D) signed legislation to count prisoners at their last known home address if they are held in state or federal prisons and were state residents before they were incarcerated.

Realistically, according to this Washington Post story, the law will have the most impact on local and state legislative boundaries because congressional districts are too large to be affected. Baltimore is expected to benefit the most from the change, but Western Maryland is expected to lose clout. Many legislators from rural areas opposed the bill.

The bill was praised in a New York Times editorial and by Prisoners of the Census, a blog run by the Prison Policy Initiative, an organization that has advocated for changing the way prisoners are counted using census data.