Definition of the word mainline

The term "mainline" originates from the railroad industry in the mid-19th century. At the time, railroads had multiple lines that branched off from a central hub, similar to the human body's circulatory system. The main line, or the primary route, was the artery that carried the majority of the traffic and was the most direct route between two points. As the use of the term "mainline" spread beyond railroads, it began to describe other things that represented the core or primary element, such as the main branch of a political party or the mainline Protestant denominations that grew out of the Protestant Reformation, like the Episcopal Church, Presbyterian Church, and United Methodist Church. Today, the term "mainline" is used to refer to various aspects of society and culture, including drugs, living circumstances, places for socializing, and economic status, to signify the central or most prestigious element.