It may be hard to believe, but there are big cities in the US where 30 to 40 percent of residents have no Internet service at all. And among those who are online in America’s worst-connected cities, a sizable percentage get by with only cellular Internet.

That’s according to 2013 census data compiled by Bill Callahan, director of Connect Your Community 2.0, a group promoting Internet access for residents of Cleveland, OH, and Detroit, MI.

Callahan published charts on his blog yesterday showing how many households lack Internet access in the 25 worst connected cities in the US (out of 176 that have at least 50,000 households). In Laredo, TX, 40.2 percent of the 65,685 households have no Internet access, not even mobile broadband on a phone. Detroit was second in this list with 39.9 percent of households lacking Internet. In all 25 cities, at least 29.8 percent lacked Internet access. The 25 cities varied in size from 52,588 households (Kansas City, KS) to 255,322 households (Detroit).