In major metropolitan areas across the U.S., unequal access to the Internet is cutting some people off from a better future. Citizens on the wrong side of the digital gap are losing out on economic, educational and social opportunities.

It's not just a technical problem for the 21st century.

"This is a civil rights issue," said Bill Callahan, director of Connect Your Community .

"Low-income people, people with less than a high school education and older people are the groups in any population who are least likely to have an Internet connection at home, he said.

Callahan's group advocates for digital access and literacy in greater Cleveland and Detroit. In those cities -- and others from Baltimore to New Orleans, from Miami to Glendale, Arizona -- as many as 30 to 40 percent of residents can't easily get online, according to 2013 data.

Rural areas have a fairly well-known set of digital access problems that include high cost and sluggish speeds due to the lack of broadband infrastructure. But in suburban and metro areas, libraries are typically cited as a the saving grace for residents who lack online access at home.

That's not good enough in our wired world. "If the best someone can do is point you to the library, thats basically 'separate but equal,' said Callahan, making a pointed reference to the very argument that the Supreme Court once declared didn't justify segregated schools.

In Detroit, nearly 40 percent of residents have no Internet service, not even via smartphones. That abysmal rate was noted in a recent New York Times story detailing how lack of access has stymied economic recovery for some people.

Detroit resident Julie Rice told the paper about her struggle to network, complete training videos and fill out online job applications with her limited connectivity.

Ive come to believe Internet is a human right," Rice said. "Its clearly a huge disadvantage if you dont have it.

Underscoring the importance of universal access, the Federal Communications Commission last year declared that broadband service is a public utility akin to electricity or telephone service.

In all but the most rural areas, the problem isn't a lack of infrastructure, said Callahan. As with so many other civil rights issues, the problem is economics.

"The idea that you cant get Internet connection in a city because theres no Internet available is almost never true, he said. "People can get AT&T DSL in their homes any place in Detroit they just cant afford it."

Without the Internet, poor people can be stuck on the wrong side of the door to opportunity.

"The 40-year-old guy who cant apply for a job now because he cant get online would have no problem 10 years ago," Callahan said. "He can still do the job. All thats changed is the system to get the job."

This hypothetical man all too often gets blamed for not being employed. Yet Callahan said, This is not a failure on his part."

Robert Shimkoski of the Detroit Employment Solutions Corporation , which helps connect jobseekers with employers in that city, said a lack of Internet access can trap low-income people in a vicious cycle.

"Its increasingly difficult to find an employer who will take a physical application over an online app," Shimkoski said. "And if you cant get online, you cant get the resources to understand where you can go to get that connection to help."