Most vanished frontier buildings stay vanished because nobody bothered to draw them. Bent's Fort was lucky. In the fall of 1845, a twenty-five-year-old Army topographical engineer named Lt. James Abert took shelter inside the walls while recovering from fever, and he passed the weeks the way bored junior officers did in those days - by sketching everything in sight. His pen-and-ink drawings and watercolors of the fort, finished in 1845 and 1846, included measured plans: door widths, wall heights, the arrangement of rooms around the placita. He could not have known that he was making the blueprints for a building that would not exist for another 130 years. Without Abert's sketchbook, there would be no reconstruction worth the name.

Abert's drawings showed what the fort looked like. The dirt showed where everything went. Archaeologist Jackson W. Moore arrived in 1963 and spent three summers excavating the site, eventually pulling roughly 35,000 artifacts from the soil - trade beads, gun parts, china, bone buttons, the small detritus of a place where Cheyenne, Mexican, French, and Anglo lives intersected daily. The dig confirmed the fort's footprint, sorted out which room was the kitchen and which was the council room, and gave the eventual builders something Abert's sketches could not provide: certainty about scale. By the time historian Dwight E. Stinson finished tracking down more than twenty eyewitness journals, the project had three independent records of the same building. They mostly agreed.

The reconstruction crew faced a problem that would have amused the original builders: adobe construction is a lost art in modern Colorado. They had to relearn it. At peak production the workers were pressing 4,000 adobe bricks a day, and the finished fort consumed 160,000 of them. Eight hundred cottonwood trees were felled for the heavy roof beams. More than 112,000 linear feet of ponderosa pine went into the smaller framing. The two hexagonal bastions rose first, then the long curtain walls, four feet thick and fifteen feet high, exactly as Abert had drawn them. There was inevitable guesswork in places - paint colors, certain door details, the precise look of furniture - but the bones are right. Stand in the placita on a hot afternoon and the adobe is cool against your back, just as it was for William Bent.

Today the fort is a working performance. Park rangers and volunteers in 1840s clothing tend the blacksmith forge, set the kitchen fires, work the carpenter's bench, and answer questions in the slightly archaic register of people pretending the year is 1846. Children handle buffalo hides. Visitors learn to identify trade goods - the beads strung in particular colors that Cheyenne customers preferred, the iron pots, the bolts of red trade cloth. On big event weekends the fort fills with mountain-man re-enactors who set up wedge tents in the meadow outside, fire flintlocks at sunrise, and stay in character around the cookfires. It is unapologetically a museum, but a peculiarly immersive one. The hammer ring, the smell of woodsmoke, the bite of adobe dust - those parts, at least, are not pretend.

Bent's Old Fort National Historic Site sits eight miles northeast of La Junta, Colorado, along the Arkansas River where the original stood. The visitor center is small; most of the experience is the fort itself, open year-round with reduced winter hours. Summer is when the living-history programs run at full strength, including a popular Fur Trade Encampment in late July or August that commemorates the dedication anniversary. The reconstruction won a Twenty-five Year Award from the American Institute of Architects for the durability of its design - high praise for a building that is supposed to look two centuries old. Colorado Springs Airport (KCOS) is 120 miles west; Pueblo Memorial (KPUB) is closer at 70 miles. Bring water and a hat; the southeastern Colorado plains do not forgive either of those oversights.