When it comes to modern engineering marvels, tunnels rank among the most impressive. They cut through mountains, dive beneath rivers, and connect regions that would otherwise be difficult to reach. The longest tunnels in the United States showcase not only technological achievement but also the country’s determination to make travel faster, safer, and more efficient. From highway tunnels carrying millions of vehicles every year to massive railroad tunnels that shaped commerce, here are the ten longest tunnels in America.
1. Delaware Aqueduct – 85 miles
The Delaware Aqueduct is the longest tunnel in the United States and one of the longest in the world. Located in New York, this water supply tunnel stretches an astonishing 85 miles. Built in the mid-20th century, it delivers nearly half of New York City’s drinking water from the Catskill Mountains.
2. Cascade Tunnel – 7.8 miles
Located in Washington State, the Cascade Tunnel runs 7.8 miles through the Cascade Range. Originally constructed in 1900 and later replaced in 1929, it remains a crucial railroad tunnel for freight and passenger trains traveling through the region.
3. Hoosac Tunnel – 4.75 miles
Nicknamed the “Great Bore,” the Hoosac Tunnel in Massachusetts runs 4.75 miles through the Hoosac Range. Completed in 1875 after more than 20 years of work, it was one of the longest tunnels in the world at the time and is still used by freight trains today.
4. Lincoln Tunnel – 1.5 miles
The Lincoln Tunnel connects midtown Manhattan, New York City, to Weehawken, New Jersey, beneath the Hudson River. Measuring 1.5 miles in length, it consists of three tubes and is one of the busiest tunnels in the United States, carrying hundreds of thousands of vehicles daily.
5. Eisenhower Tunnel – 1.7 miles
High up in the Colorado Rockies, the Eisenhower Tunnel is one of the highest-altitude vehicular tunnels in the world. At 1.7 miles long and over 11,000 feet above sea level, it provides a critical route through the Continental Divide along Interstate 70.
6. Ted Williams Tunnel – 1.6 miles
Part of Boston’s “Big Dig” project, the Ted Williams Tunnel stretches 1.6 miles under Boston Harbor. It connects South Boston to Logan International Airport and remains a vital transportation link in New England.
7. Brooklyn–Battery Tunnel (Hugh L. Carey Tunnel) – 1.7 miles
This New York City tunnel, officially renamed the Hugh L. Carey Tunnel, is the longest continuous underwater vehicular tunnel in North America. At 1.7 miles, it links Manhattan to Brooklyn beneath the East River.
8. Anton Anderson Memorial Tunnel – 2.5 miles
Located in Alaska, the Anton Anderson Memorial Tunnel is unique because it serves both trains and vehicles. At 2.5 miles, it is the longest highway tunnel in North America, connecting Whittier to the Seward Highway.
9. Mount Baker Ridge Tunnel – 1.1 miles
Seattle’s Mount Baker Ridge Tunnel is notable for being the world’s largest-diameter soft-ground bored tunnel at the time of construction. At 1.1 miles, it plays a crucial role in Interstate 90, allowing traffic to pass beneath Mount Baker Ridge.
10. Holland Tunnel – 1.6 miles
Completed in 1927, the Holland Tunnel was the first underwater vehicular tunnel built under the Hudson River. Spanning 1.6 miles, it connects Lower Manhattan to Jersey City, New Jersey, and is still heavily used today.
Why the Longest Tunnels in the U.S. Matter
The longest tunnels in the United States are more than just transportation routes. They are feats of engineering that overcome natural barriers, reduce travel times, and connect communities. From delivering water to powering trade routes, these tunnels showcase American ingenuity at its best.
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