What affect both the united states and canada?

What event was one of the greatest factors that led to massive emigration from ireland to the united states in the mid—1800s

Which of the following was a key accomplishment of the people of songhai? a. they had a strong military and became the largest empire in west africa. b. they established a center of islamic scholarship. c. they worked with iron and prospered from the gold-salt trade. d. they dominated in the trade of ivory, enslaved people, and animal skins.

How would having more railroad tracks be advantageous during a war