Until now, drivers were barred from writing text messages while negotiating traffic but permitted to read them.
"Our police are well aware of this law," said state police spokesman Greg Shipley. "They will be immediately enforcing it."
It's bound to be the most noticeable of several hundred new laws that officially go on the books starting Saturday. Other new rules toughen penalties for drunk driving, gun possession and animal abuse.
Maryland drivers also aren't supposed to talk on their cell phones per a year-old law, but doing so is remains a "secondary offense," meaning police can only pull over a driver who is also breaking another rule.
Since the initial ban on texting an driving was put in place two years ago, police in Maryland have issued 587 warnings and 379 traffic citations, according to a database that compiles information from 76 Maryland law enforcement agencies including the state police.
Since the ban on talking on cell phones took effect, the same group of police organizations has issued 4,021 warnings and 5,227 traffic citations.
"When you are driving, your eyes should be on the road," said Sen. Jim Brochin, a Baltimore County Democrat who pushed the bill.
Drivers will still be able to use GPS systems on their phone while driving or text an emergency operator.
Drivers who are ticketed can still choose to accept guilt and pay a $70 fine (plus one point on their license). If the texting leads to an accident, accepting guilt means an automatic $110 fine and three points.
Drivers who contest the tickets and lose in court will be guilty of a misdemeanor and have to pay the full $500.