Signal Tower at Ft. Wisconsin, Va., left of lines by Mathew Brady. Original public domain image from Flickr https://www.rawpixel.com/image/8799881/photo-image-vintage-public-domainFree Image from public domain licensePowerlines amid a pine forest on a foggy winter day. Original public domain image from Wikimedia Commons https://www.rawpixel.com/image/3297221/free-photo-image-cable-cc0-cloud-pictures-imagesFree Image from public domain license[Untitled photo, possibly related to: Crossing towers and the Columbia River at Bonneville Dam, Oregon] by Russell Lee https://www.rawpixel.com/image/12152822/image-plant-art-skyFree Image from public domain license"Making a trip," pulling up old pipe to change bit on drilling pipe on the bottom of oil well at C.C. Graber pool of… https://www.rawpixel.com/image/12248405/photo-image-person-sky-airplaneFree Image from public domain license[Untitled photo, possibly related to: Crossing towers and the Columbia River at Bonneville Dam, Oregon] by Russell Lee https://www.rawpixel.com/image/12144176/image-art-sky-vintageFree Image from public domain licenseCentral tower from which materials used in construction of Shasta Dam are distributed. Shasta County, California by Russell… https://www.rawpixel.com/image/12144651/image-art-sky-vintageFree Image from public domain licenseA mother and child; advertising the prevention by German mothers of the transmission of tuberculosis to and from their… https://www.rawpixel.com/image/13985815/image-paper-face-personFree Image from public domain license[Untitled photo, possibly related to: Crossing towers and the Columbia River at Bonneville Dam, Oregon] by Russell Lee https://www.rawpixel.com/image/12151674/image-plant-art-skyFree Image from public domain license[Untitled photo, possibly related to: "Making a trip," pulling up old pipe to change bit on drilling pipe on the bottom of… https://www.rawpixel.com/image/12248659/photo-image-plant-person-skyFree Image from public domain licenseOil well derricks and pumps in Moundridge area near McPherson, Kansas. Sourced from the Library of Congress. https://www.rawpixel.com/image/12248646/photo-image-person-sky-technologyFree Image from public domain licenseLifting casing upon the derrick to finish a water well for irrigation purposes on farm near Garden City, Kansas by Russell… https://www.rawpixel.com/image/12110091/image-person-art-skyFree Image from public domain license[Untitled photo, possibly related to: Drilling operations and derricks. Kilgore, Texas] by Russell Lee https://www.rawpixel.com/image/12174752/image-cloud-art-skyFree Image from public domain license