<P> Below is a list of so - called megaprojects that are among the most expensive in U.S. history . </P> <P> The following list includes projects to build new highways or improve existing ones, including roadways, bridges, and tunnels . It includes only projects that are underway or completed . Additionally, projects with multiple independent segments (e.g., I - 69 Indiana - Texas Extension, Trans - Texas Corridor) are not included, though individual segments may or may not make the list . Costs shown below exclude financing costs . </P> <Table> <Tr> <Th> Date </Th> <Th> Price (nominal) </Th> <Th> Reference Year </Th> <Th> Price (ref . year) </Th> <Th> Price (2016 $) </Th> <Th> Project </Th> </Tr> <Tr> <Td> 1992--2006 </Td> <Td> $14.6 billion </Td> <Td> 1982 </Td> <Td> $8.08 billion </Td> <Td> $20.1 billion </Td> <Td> Big Dig, Boston, Massachusetts </Td> </Tr> <Tr> <Td> 2002--2013 </Td> <Td> $6.416 billion (est .) </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> San Francisco--Oakland Bay Bridge East Span Replacement, San Francisco / Oakland, California </Td> </Tr> <Tr> <Td> 1988--2002 </Td> <Td> $5.0 billion </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Mon--Fayette Expressway, southwest Pennsylvania and northern West Virginia </Td> </Tr> <Tr> <Td> 2005--2020 (est .) </Td> <Td> $4.1 billion (est .) </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Ohio River Bridges Project, Louisville, Kentucky, and southern Indiana </Td> </Tr> <Tr> <Td> 2001--2007 </Td> <Td> $3.6 billion </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Central Texas Turnpike, area around Austin, Texas </Td> </Tr> <Tr> <Td> 2007--2011 </Td> <Td> $2.57 billion </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Intercounty Connector, Montgomery County, Maryland </Td> </Tr> <Tr> <Td> 1999--2008 </Td> <Td> $2.5 billion </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Woodrow Wilson Bridge Replacement, Washington, D.C., Northern Virginia, and southern Maryland </Td> </Tr> <Tr> <Td> 2015--2021 </Td> <Td> $2.3 billion (est .) </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> I - 4 Ultimate corridor reconstruction, Orlando, Florida </Td> </Tr> <Tr> <Td> 2012--2015 </Td> <Td> $4.25 billion </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Alaskan Way Viaduct replacement tunnel, Seattle, Washington </Td> </Tr> <Tr> <Td> 2008--2018 </Td> <Td> $1.8 billion (est .) </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Interstate 69 Extension SIU #3, Evansville to Indianapolis, Indiana </Td> </Tr> <Tr> <Td> 2013--2021 </Td> <Td> $1.6 billion (est .) </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> Wekiva Parkway, Orlando, Florida </Td> </Tr> <Tr> <Td> 2001--2016 </Td> <Td> $1.4 billion (est .) </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> I - 95 New Haven Harbor Corridor Reconstruction, New Haven, Connecticut </Td> </Tr> <Tr> <Td> 1991--2003 </Td> <Td> $1.2 billion </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> E-470, Denver, Colorado </Td> </Tr> <Tr> <Td> 1933--2007 </Td> <Td> $37 million </Td> <Td> 1937 </Td> <Td> $37 million </Td> <Td> $616 million </Td> <Td> Golden Gate Bridge </Td> </Tr> <Tr> <Td> 2015--2028 </Td> <Td> $67.6 billion (est .) </Td> <Td> 2013 </Td> <Td> $54.9 billion </Td> <Td> $56.4 billion (est .) </Td> <Td> California High - Speed Rail, Phase 1, California </Td> </Tr> <Tr> <Td> 1863--1869 </Td> <Td> $124,548,691 </Td> <Td> 1873 </Td> <Td> $124,548,691 </Td> <Td> $2.49 billion </Td> <Td> First Transcontinental Railroad </Td> </Tr> <Tr> <Td> 1956--2017 </Td> <Td> $425 billion </Td> <Td> 2006 </Td> <Td> $425 billion </Td> <Td> $505 billion </Td> <Td> Interstate Highway System </Td> </Tr> <Tr> <Td> 2003--2008 </Td> <Td> $1.5 billion </Td> <Td> </Td> <Td> $2.8 billion (2008) </Td> <Td> $3.1 billion </Td> <Td> I - 10 Katy Freeway Expansion (Interstate 10 in Texas) </Td> </Tr> <Tr> <Td> 1959--1964 </Td> <Td> $320 million </Td> <Td> 1964 </Td> <Td> </Td> <Td> $2.44 billion </Td> <Td> Verrazano - Narrows Bridge </Td> </Tr> </Table> <Tr> <Th> Date </Th> <Th> Price (nominal) </Th> <Th> Reference Year </Th> <Th> Price (ref . year) </Th> <Th> Price (2016 $) </Th> <Th> Project </Th> </Tr>

What was the largest single public works project in the history of america