All these isthmus routes, moreover, needed improvement.

Capital must be induced to do the work, and one necessary inducement was a guarantee of stable conditions of investment.
This isthmus route became for a time the prime object of American diplomacy.

The United States made in 1846 satisfactory arrangements with the Republic of New Granada (later Colombia), across which lay the most southern route, and in 1853 with Mexico, of whose northern or Tehuantepec route many had great expectations; but a further difficulty was now discovered.

The best lanes were those of Panama and of Nicaragua.

When the discovery of gold in California in 1848 made haste a more important element in the problem, "Commodore" Vanderbilt, at that time the shipping king of the United States, devoted his attention to the Nicaragua route and made it the more popular.