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Landmark day • Thursday, April 15, 1915

April 15, 1915: Roosevelt Lake Fills for the First Time

Four years after Roosevelt himself dedicated the dam, the lake behind it finally reaches the spillways — and the Valley learns what a full reservoir feels like.

Illustrated plaque for April 15, 1915 in Scottsdale history SCOTTSDALE APRIL 15 1915 STATEHOOD & THE FARM TOWN

What happened

A wet winter in the Salt and Verde watersheds filled Roosevelt Lake to its 1915 capacity for the first time, and on the evening of April 15 water began pouring over the spillways on both sides of the dam. The reservoir had sat roughly half full since the dam's completion in 1911. Crowds drove up the Apache Trail to watch the overflow, and the Reclamation Service declared the project's storage fully proven.

Why it matters

A dam is only insurance once the reservoir is full. With Roosevelt Lake brimming, the Valley's farmers had, for the first time in the settlement's history, more than one season of water banked against drought — the security that let Scottsdale's growers plant boldly when wartime cotton prices arrived two years later.

The half-full years

Roosevelt Dam had been finished for four years, and in those four years it had never done the one thing it was built for. When the last stone went in on February 6, 1911, and Theodore Roosevelt came to dedicate the dam that March, the lake behind it stood at a fraction of capacity; the dry years that had driven the Valley to Washington in the first place did not end on schedule. Through 1911, 1912, 1913, and 1914 the reservoir sat roughly half full — enough to make irrigation reliable on the benchland where Scottsdale’s farms sat, but not enough to prove the design, and not enough to silence the skeptics who had said a dam that size would never see its own spillways.

The winter of 1914–15 settled it. Heavy rain and snow in the mountains sent the Salt and Tonto Creek running high for weeks, and the lake rose past every mark it had reached before. On the evening of April 15, 1915, water crossed the crest of both spillways and began falling into the canyon below the dam. The Reclamation Service had built the dam to the world’s tallest masonry profile, 280 feet, and the lake it now held was the largest artificial body of water in the country.

What a full lake changed

The Valley treated it as a holiday. Motorists took the Apache Trail up to watch the overflow; the newspapers ran the spill as a front-page vindication. Beneath the celebration was a practical shift that mattered more to a farm village like Scottsdale than to the crowds. A full Roosevelt Lake meant several seasons of water in the bank, which meant a grower could plant on the assumption of a harvest rather than a hope of one. The town’s fields that year were in alfalfa, grain, dates, and orchards — the cautious, diversified spread the drought generation had learned to trust.

Two years later, when America entered the war and long-staple cotton went from a crop to a strategic material, that stored water was what let Scottsdale’s farmers rip out the orchards and plant cotton to the fencerows without fear of a dry summer. The boom that followed is the story of April 1917. The rest of this year sits at 1915, and the farm-town decade in the 1910s chapter.