Major American construction projects symbolized ambition but faced delays, costs and engineering challenges.
1. California High-Speed Rail
First proposed in the early 2000s, California’s high-speed rail project was intended to connect Los Angeles and San Francisco with trains traveling hundreds of miles per hour.
Construction began in 2015, but the project has faced repeated delays, legal challenges, and funding issues. As of the mid-2020s, it remains incomplete, with only partial segments under construction. Estimated costs have risen from around $33 billion to well over $100 billion.
2. Boston’s Big Dig
Boston’s Central Artery/Tunnel project was designed to replace an aging elevated highway with underground tunnels.
Construction began in 1991 and was largely completed in 2007. Originally estimated at about $2.8 billion, the final cost ballooned to more than $14 billion, making it one of the most expensive highway projects in U.S. history.
3. Washington Metro
The Washington Metro was first planned in the 1960s as a solution to growing traffic around the nation’s capital.
The system opened in 1976, with major expansions continuing for decades afterward. While much of the original system was completed by the early 2000s, ongoing extensions and major repairs have continued. Total system costs have exceeded $25 billion over time.
4. Interstate Highway System
Launched in 1956 under President Dwight D. Eisenhower, the Interstate Highway System was designed to connect the entire United States with a vast network of high-speed roads.
Although officially declared “complete” in 1992, construction and expansion have continued for decades due to population growth, urban sprawl, and infrastructure upgrades. The system ultimately cost over $500 billion when adjusted for inflation, making it one of the largest public works projects in world history.
5. New York City’s Second Avenue Subway
Plans for a Second Avenue Subway line date back to the early 20th century.
After multiple cancellations and restarts, the first phase finally opened in 2017—nearly 100 years after initial proposals. The first segment cost about $4.5 billion, making it one of the most expensive subway lines per mile ever built.
6. Denver International Airport
Denver International Airport opened in 1995 after years of delays and controversy.
Construction began in 1989 and was completed in 1995, but the project faced major setbacks, including its failed automated baggage system. The total cost reached approximately $4.8 billion, far above initial estimates.
