The US Census counts prisoners as residents of whatever town they happen to be incarcerated in, rather than where they are from. This has, for decades, resulted in small, rural towns that house prisons having greater representation in Congress than they would with their populations alone. What makes that even more unfortunate is those places are typically some of the more conservative areas, and the undue political influence they get to wield is rather unsympathetic to the plight of most prisoners. Political power gets transferred out of the cities, where a lot of minority citizens live, into rural areas whose interests often run counter to those of the poor and disadvantaged minorities who lose out.
The title link is to a brief article that pretty clearly demonstrates the problem; a small town of less than 5,000 residents in Georgia will be counted as having nearly 7,700 because of the population of immigration detainees housed there, even though many of those detainess will spend 2 months or less at the facility. That count will translate into more federal funding for the area than it really needs or deserves, and could possibly result in a re-districting measure that could give them an additional Congressional seat. Which is just great.