In the 1850s, Baltimore's 170,000 residents had few options when it came to getting around town. Before the decade's end, however, the omnibus--an urban version of the stagecoach--emerged as Baltimore's first mass-transit vehicle. Horsecars followed, then cable cars, and ultimately electrically powered streetcars. Recognizing the need for cohesion, the city's myriad transit providers merged into a single operator. United Railways and Electric Company,...