City and county police and fire police responded to Wesel and Garland Groh boulevards in Hagerstown, Huyetts Crossroads and the Williamsport area to direct traffic and keep order after electricity in those areas failed shortly after 8 p.m., a county dispatcher said.
The Washington County Sheriff's Department on Western Maryland Parkway had to rely on a back-up generator for power.
Emmanuel Munoc, owner of El Ranchero Mexican Restaurant at 1580 Wesel Boulevard, said his customers ate their dinners by candlelight after the lights went out.
He didn't have a back-up generator and had to turn customers away, he said.
"Friday is one of my busiest nights," he said. "I lost some business."
A few doors up at the Martin's Food Market, employees were escorting shoppers to their cars with flashlights, cashier Jason Conte said.
The outage disrupted traffic lights along Garland Groh Boulevard near the Centre at Hagerstown, including the traffic signal at the busy U.S. 40 intersection, police said.
Lights went out at such Centre stores as the Wal-Mart Supercenter, which lost power about 8:10 p.m. and had to rely on a back-up generator, an employee said.
The outage affected traffic lights extending from Wesel Boulevard at Burhans Boulevard to about the 1600 block of Wesel Boulevard, city police said.
Wesel Boulevard street lights were out, and businesses such as Lowe's of Hagerstown and Martin's Food Market resorted to back-up generators after losing power shortly after 8 p.m., store managers said.
Nearby Massey Boulevard businesses such as Wonder Book & Video, Valley Mall and The Ground Round restaurant had electricity, employees said.
Pilot Travel Center on Md. 63 just north of Williamsport lost electricity, as did the Sheetz convenience store at the intersection of Md. 63 and U.S. 40 in Huyetts Crossroads, store employees said.
The traffic signal at that intersection was not affected, state police said.
Staff writer Richard F. Belisle contributed to this story.