The meat was packed tightly at the bottom of the car to keep the center of gravity low and to prevent the cargo from shifting. Chase's design proved to be a practical solution to providing temperature-controlled carriage of dressed meats, and allowed Swift & Company to ship their products all over the United States, and internationally. This radically altered the meat business. Swift's attempts to sell this design to the major railroads were unanimously rebuffed as the companies feared that they would jeopardize their considerable investments in stock cars and animal pens if refrigerated meat transport gained wide acceptance. In response, Swift financed the initial production run on his own, then — when the American railroads refused his business — he contracted with the GTR (a railroad that derived little income from transporting live cattle) to haul them into Michigan and then eastward through Canada. In 1880, the Peninsular Car Company (subsequently purchased by American Car & Foundry) delivered to Swift the first of these units, and the Swift Refrigerator Line (SRL) was created. Within a year the Line's roster had risen to nearly 200 units, and Swift was transporting an average of 3,000 carcasses a week to Boston. Competing firms such as Armour and Company quickly followed. By 1920 the SRL owned and operated 7,000 ice-cooled rail cars. The General American Transportation Corporation assumed ownership of the line in 1930.