Final answer:
Expansionists in the South were active in the early 1850s, with various attempts to gain territory and secure trade routes. William Walker captured Nicaragua, the Clayton-Bulwer Treaty addressed an important canal route, Commodore Matthew Perry opened Japan to trade, and the Ostend Manifesto failed in the attempt to acquire Cuba from Spain.
Step-by-step explanation:
Expansionists, especially in the South, had a field day in the early 1850s. William Walker gained control of Nicaragua, while the Clayton-Bulwer Treaty resolved disputes over a potential canal route across the Isthmus of Panama. Commodore Matthew Perry opened Japan to trade ties in 1854. Plans to grab Cuba from Spain were foiled when the Ostend Manifesto failed.