1. Topographic sheets. United States, topographic and geologic index map showing progress in surveying and engraving topographic maps and publishing geologic folios to Jan. 1, 1911, scale 1:2,500,000; with inset, Alaska, index map showing areas covered by topographic maps, Jan. 1911, scale 250 m.=1.5 in. Bookmark Corporate/Agency Authors: Geological Survey and Interior Department Publisher: Geological Survey Date: 1910 [1911] first published 1890