I'm creating a developed country in South America with its development similar to that of Canada or Australia (little behind the US). See the map below - the white line surrounds fertile and populated areas.
Its capital had always been in what is now Buenos Aires (which is also actually the capital of Argentina) thanks to its extremely strategic location.
But with the advent of railways in 1830s-1850s I wonder whether to build a new seaport and (maybe a new capital) city in Punta Indio - an uninhabitated and swampy site located 130 km (80 mi) from Buenos Aires toward the ocean.
The reason is that the ships wouldn't need to go so much inland anymore. But instead, the goods and the passengers would transfer from ships to trains in Punta Indio because trains were much faster than ships. Also, it would be much closer to Montevideo, another country's very important seaport.
Another good reason is that Punta Indio has much milder climate than hot Buenos Aires thanks to proximity of cold ocean currents. And that affects human workforce efficiency considerably as well.
But how about the ship vs train transportation cost and the overall efficiency of this plan?