What 19th century construction projects provided the greatest boom to economic unification in both the U.S. and Canada?
AThe building of massive dams and hydroelectric projects
BThe building of telephone and telegraph systems
CThe building of transcontinental railroads
DThe building of highways and bridges
AThe building of massive dams and hydroelectric projects
BThe building of telephone and telegraph systems
CThe building of transcontinental railroads
DThe building of highways and bridges