It was when the united states purchased the states around nebraska and missouri.
I believe the answer is: Africa and Mexico
New imperialism refers to the era when European made various efforts to gain new territory after the industrial revolution.
Africa and Mexico became their main target because both of these territory are rich in natural resources that are popular during industrial revolution. Africa was known for their metal reserves while mexico was known for their Oil and crops
The Black Death is known as one of the deadliest and widespread pandemics in history. It peaked in Europe between 1348 and 1350 and is thought to have been a bubonic plague outbreak caused by Yersinia pestis, a bacterium. It reached the Crimea in 1346 and most likely spread via fleas on black rats that travelled on merchant ships. It soon spread through the Mediterranean and Europe. The Black Death is thought have destroyed 30% to 60% of Europe's population - experts say it took 150 years for Europe to recover its population size. The plague came back several times until the 19th century, when it left Europe for good. Most victims died with two to seven days of becoming infected.
An option to consider is, Persia.