根据一段文本生成摘要。
提供以下段落的文本：In 1950, a locomotive named “Big Boy” was unveiled by the Union Pacific Railroad in the United States. It was over 85 feet long and weighed more than one million pounds. It was designed to haul heavy freight trains over the Rocky Mountains of Wyoming and Utah. The locomotive was retired in 1961 and several examples are now preserved in museums across the US.
"Big Boy" locomotive, introduced in 1950 by Union Pacific Railroad, was specifically designed to carry heavy freight over the Rocky Mountains of Wyoming and Utah. With a length of 85 feet and a weight exceeding one million pounds, the locomotive was retired in 1961, but some examples are now preserved in museums across the US.