Per Wikipedia, the Golden Gate Bridge was proposed in 1917, approved by the state for design in 1923, funded in 1930, started construction in 1933, and completed in 1937.

The reason modern projects take so long is that so many of them are stuck in design or awaiting funding stage for what feels like interminable ages; once the construction phase starts, they tend to go fairly quickly. But if you look at projects 100 years ago, well, they also seem to have fairly lengthy pre-construction timelines. It's just that we conveniently forget about those when we look back on them nowadays.