During the Silver Age of Alpinism in the late 19th century, most of the unclimbed major mountaineering objectives were reached. With the closing of the age of discovery of mountain peaks, interest shifted towards finding enjoyable ways to climb already-ascended mountains. In the 1890s, Sir Hugh Munro created Munro list of the highest peaks of Scotland; summiting the peaks on such lists soon became known as peak bagging. Peak bagging was brought to the United States by Robert and George Marshall in 1918.