By the end of 1913, trains were arriving at Craig, CO, over a recently completed extension of the former Denver, Northwestern & Pacific Rwy, which had been reorganized as the Denver & Salt Lake by the time of its completion. However, the funding had once again evaporated for the continued trek westward from Craig towards the goal of Salt Lake City. World War I would start only a year later, with the United States entry into combat only a few years later. Funding was scarce and revenue scarcer, and as such Erb was forced to resign 16-Sep-1917. While the USRA had poured over 1.3 million dollars into the line for war needs, the line came out from under government control still seriously hemmoraging red ink. The labors of hauling freight over Rollins and keeping it open through the winter were chewing up almost a million dollars or more a year that the line didn't have. Meanwhile, on the first day of 1920, the Burlington was threatening to rebuild the narrow gauge Colorado and Southern up from Denver to the Main Range and build the main bore themselves.

By 1921, the road was once again back in the bankruptcy courts, this time fighting for its very existance. Scrapping was a real possibility, as the road hadn't turned a profit and was perpetually failing to service its debt. Even the receives of the time - Boettcher and Freeman - were discussing terminating service with the state Public Utilities Commission. However, with the line carrying almost 24,000 loaded cars in 1920, terminating service wasn't really an option. A solution to the perpetual deficit needed to be found. The courts ordered wages reduced as a cost reduction measure, feeling that the men were paid wages out of line with other railroads, but that wasn't the road's real problem. The real money pit was Rollins Pass, and it simply had to go. Anything with four percent grades and blizzards that could strand trains for weeks at a time needed to be bypassed if the railroad was ever succeed.

As it would unfold, the Moffat's turning point would also be one of Colorado's worst natural disasters. A series of early summer thunderstorms in 1921 created a massive deluge of floodwaters that turned the normally placid Arkansas River and tributaries into raging, destructive torrents. On the evening of June 3, these torrents ripped through Pueblo, raising the Arkansas over 12 feet above flood stage and destroying everything in a mile-wide swath through the heart of the city. After this calamity, Pueblo wanted the state to put in flood control on the Arkansas, and they got it - with one little catch. Two bills were introduced in a special Colorado General Assembly session on 8-Apr-1922 - one to fix the Arkansas River's bad temper permanently, and the other to finally build the Main Range tunnel. Thanks to a great deal of political wrangling, with the northern representatives not caring about Pueblo's flood problems and Pueblo's representatives opposing the tunnel, both bills finally passed.

The Main Range Tunnel, now officially named the Moffat Tunnel by the legislation in honor of David Moffat's vision, would finally be built. A 6.2 mile bore straight through the main range of the Rockies, the tunnel would cut off 2500 feet of climbing and descending, 23 miles of extra track, and most of all some twelve or more hours of grueling, dangerous railroading over Rollins Pass. There would no longer be the threat of trains trapped for days or weeks by blizzards or deep drifting snow. Instead, freight and passengers would cruise safely under the Rockies in a matter of minutes. Started in 1924, the first train passed through the massive hole only four years later, on 14-Feb-1928.

Immediately following the stroke of good luck on the tunnel, freight also began to pour over the Moffat Road in 1923. The Routt County coal mining industry was booming, and oil had been discovered at a depth of only half a mile just south of Craig. Aside from the drilling and mining gear going west, the raw resources were flowing eastward. Thirty tankers of oil a day moved by 1924, and that number doubled by 1925. By 1926, Texaco had built a small refinery in Craig, and as such the D&SL was also hauling refined oil products eastward across the Divide. Financial prospects for the line, having been dire and bleak only six years before, were now much, much brighter. The darkest days of the Moffat Road were past, and the Denver & Salt Lake Railway was incorporated in Jan 1926 to assume the still-in-receivership Denver & Salt Lake Railroad's assets.

The Moffat Tunnel was a monumental step forward, but with the D&SL in its current configuration (ending at Craig, CO), it was still a very expensive hole on a railroad that went nowhere important. The D&SL connected with no other roads or major cites west of the Continental Divide. So, as part of the Moffat Tunnel project, the D&SL and D&RGW were strongly urged to look at linking their lines. The most likely point for this was the easy 45 miles of water-level route between Bond, CO, and a point near the confluence of the Grand and Eagle Rivers on the D&RGW's standard gauge mainline over Tennessee Pass.

This route, to eventually be known as the Dotsero Cutoff, wouldn't be built until several years after the Moffat Tunnel, but was eventually pushed through as a condition of the D&RGW's purchase of the D&SL in 1930. In June of 1934, the two systems were linked, and what we know today as the Rio Grande's standard gauge network was finally completed.

The railroads remained separate on paper for almost two more decades, but during that time there was no doubt things had changed. The Rio Grande wasted little time in bringing the old Moffat Road up to standards - lining tunnels, laying heavier rail, and realigning sections with better grading and straighter routes. The D&RGW had acquired a much faster route from Denver to Salt Lake, and was doing everything possible to take advantage of it. Eventually, the D&SL itelf would fade into D&RGW corporate history. Finally, on 11-Apr-1947, the D&SL was officially folded into its parent road and ceased to exist.