The North Side Main Line is a branch of the Chicago "L" system that is used by Red, Purple, and Brown Line trains. As of 2012, it is the network's busiest rail branch, serving an average of 123,229 passengers each weekday. The branch is 10.3 miles (16.6 km) long with a total of 21 stations, from Howard Street in Rogers Park down to Lake Street in Chicago's Loop. The branch serves the north side of the city 24 hours a day, seven days a week.