It’s happening again, and this time you can blame your smartphone.

More than a decade after Maryland last added area codes, two of them — 410 and 443 — are running out of numbers, the state’s Public Service Commission announced Wednesday.

Starting March 24, Baltimore residents and residents of Anne Arundel, Calvert, Howard and other counties in eastern Maryland will have to get used to dialing a new trio of digits: 667.

“My understanding is the proliferation of mobile devices is the main cause,” said Douglas Nazarian, chairman of the Public Service Commission.

“Just think how many numbers you have where people can reach you. I have four or five,” he added. “There are just more devices now that require a phone number.”

This isn’t the first time Maryland has had to add an area code. According to the North American Numbering Plan, the organization that manages area codes and offers “area code relief,” 301 was Maryland’s first — created in 1947 — and among the first in the nation.

In 1991, the state added a second area code, 410. The new code was implemented as a “split”: Western and central areas of Maryland, including the Washington suburbs, retained the 301 code, and 410 went into effect in eastern Maryland.

Then in 1997, instead of splitting, which would have required many residents to change their phone numbers, the state elected to “overlay” the 240 area code in the 301 region and 443 in the 410 region.

“Those were the huge cultural shifts,” Nazarian said, because it became necessary to dial the area code even to reach a number that had the same area code. “Now we’re used to it. I think this transition will be underwhelming in comparison to the ’90s.”

Maryland isn’t alone in its ever-expanding code system. Nationwide, every area code generates more than 7 million unique phone numbers, which are divvied up among phone companies in blocks of 10,000. In recent years, the North American Number Plan has issued between 25 and 30 new area codes a year.

Virginia has seven area codes and one overlay: 571 in Northern Virginia overlays the state’s original code, 703. There are no overlays scheduled for the commonwealth.

The District, on the other hand, is running on a single area code that the North American Numbering Plan estimates will be “in jeopardy” around 2018.

There isn’t much that locals and locals-to-be can do about the new area code, though, and if you ask Nazarian, there is no reason they should want to.

“I don’t consider myself an expert on Maryland culture,” Nazarian said, “but here your area code is not a status thing,” although it seems to be in some other places.

New York City, for one, experienced a particularly angsty overlay in 1999, when the city ran out of numbers in the 212 area code and had to introduce the much-maligned 646.

Beyond simple inconvenience, “the real source of tsoris is sociocultural: the looming stigma of 646,” according to a 1999 Washington Post article. “Like walking slowly, wearing pastels or ordering a pastrami with mayo, it will be the mark of the outlander.”

One grim implication of the new code — that people with 212 numbers wouldn’t want to date people with 646 numbers — was even featured in an episode of “Seinfeld.”

But Nazarian said 410 and Maryland’s other area codes don’t carry the same cachet as 212, so the transition should be painless.

He said “667 might look a little funny, and people might be hesitant to answer, like, ‘Is this a local number?’ But your telephone experience is mostly unchanged.”