“If any Charter Subscriber is surprised by what turned out to be the first story in this first issue of LIFE,” the magazine’s editors wrote in the Nov. 23, 1936, issue, “he is not nearly so surprised as [we] were. Photographer Margaret Bourke-White had been dispatched to the Northwest to photograph the multimillion dollar projects of the Columbia River Basin. What the editors expected were construction pictures as only Bourke-White can take them. What the editors got was a human document of American frontier life which, to them at least, was a revelation.” Thus the men and women behind what would become one of the longest-lived experiments — and one of the greatest success stories — of 20th century American publishing introduced themselves, and their inaugural effort, to the world. In her riveting 1963 autobiography, Portrait of Myself, Bourke-White herself recalls the heady experience working for LIFE — on the debut issue, and on countless subsequent assignments for what would become one of the indispensable weeklies of the past 100 years: Margaret Bourke-White—LIFE MagazineFirst LIFE cover November 23, 1936. A few weeks before the beginning, Harry Luce called me up to his office and assigned me to a wonderful story out in the Northwest. Luce was very active editorially in the early days of the magazine, and there was always that extra spark in the air. Harry’s idea was to photograph the enormous chain of dams in the Columbia River basin that was part of the New Deal program. I was to stop off at New Deal, a settlement near Billings, Montana, where I would photograph the construction of Fort Peck, the world’s largest earth-filled dam. Harry told me to watch out for something on a grand scale that might make a cover. “Hurry back, Maggie,” he said, and off I went. I had never seen a place quite like the town of New Deal, the construction site of Fort Peck Dam. It was a pinpoint in the long, lonely stretches of northern Montana so primitive and so wild that the whole ramshackle town seemed to carry the flavor of the boisterous Gold Rush days. It was stuffed to the seams with construction men, engineers, welders, quack doctors, barmaids, fancy ladies and, as one of my photographs illustrated, the only idle bedsprings in New Deal were the broken ones. People lived in trailers, huts, coops anything they could find and at night they hung over the Bar X bar. These were the days of LIFE’s youth, and things were very informal. I woke up each morning ready for any surprise the day might bring. I loved the swift pace of the LIFE assignments, the exhilaration of stepping over the threshold into a new land. Everything could be conquered. Nothing was too difficult. And if you had a stiff deadline to meet, all the better. You said yes to the challenge and shaped up the story accordingly, and found joy and a sense of accomplishment in so doing. The world was full of discoveries waiting to be made. I felt very fortunate that I had an outlet, such an exceptional outlet, perhaps the only one of this kind in the world at that time, through which I could share the things I saw and learned. Seventy-six years after Margaret Bourke-White’s remarkable photos from the Depression-era wilds of Montana graced the pages of that very first issue of LIFE — and one of her characteristically monumental “construction pictures” (as the editors put it) served as the cover image for that issue — LIFE.com reprints the Fort Peck Dam feature in its entirety, along with a number of Bourke-White photos that did not appear in the original cover story. Here is a portrait of a community brought together by circumstance, i.e., by FDR’s New Deal, in a barren place, in an unimaginably hard time, for the express purpose of building one of the chief engineering marvels of the age. (Fort Peck Dam is still, today, the highest of all the major dams along the great Missouri River.) Bourke-White’s photos, meanwhile, capture the vast scale of the audacious project and the far more intimate scope of the human capacity for finding joy — or, at the very least, a kind of rough pleasure and fellowship — wherever one can, whatever the odds. So, while LIFE’s “charter subscribers” and its editors might have been surprised “by what turned out to be the first story” in the magazine’s history, in retrospect Bourke-White’s tale seems — with its heroic overtones, its astonishing photography and its focus on the human aspect of a superhuman effort — a perfectly apt introduction to LIFE’s mission and its method. Liz Ronk, who edited this gallery, is the Photo Editor for LIFE.com. Follow her on Twitter at @LizabethRonk.