Final answer:
Secession movements were a significant consequence of the ethnicity challenges in the Louisiana Territory period, as the controversy surrounding slavery led to divisions between northern and southern states.
Step-by-step explanation:
A significant consequence of the ethnicity challenges in the Louisiana Territory period was secession movements. These movements emerged as a result of the sectional controversy surrounding the issue of slavery in the Missouri Crisis. Northern states, seeking to gradually abolish slavery, clashed with southern states, which firmly defended the institution. This division over slavery shaped sectional identities and eventually led to secession and the outbreak of the American Civil War.