William Le Baron Jenney is considered the founder of the Chicago School of architecture, as well as the father of the American skyscraper. He served as an engineering officer during the Civil War but by 1868 was a practicing architect. His greatest accomplishments were his mammoth commercial buildings, including the Home Insurance Building in Chicago, which was one of the first buildings to use a metal skeleton. This structure, in fact, would become the archetypical American skyscraper design. Other notable accomplishments included his 16-story Manhattan Building, which was the first edifice ever to achieve that height, and the Horticultural Building, which was the largest botanical conservatory ever erected. William Holabird also assisted in the evolution of the Chicago School, beginning as a draftsman for Jenney and then founding his own practice in 1880. Holabird invented the "Chicago window," which made buildings appear to be constructed of glass.