Indiana Social Studies 8.H.18

Social Studies8th GradeHistory

The Standard

Analyze the causes and effects of the Mexican War (1846-1848).

2026 Indiana Academic Standards: K-12 Social Studies

Teacher's field guide

What Students Need to Do: Students explain why the United States and Mexico went to war, using a map and accounts of the border dispute. They describe how the peace treaty changed U.S. territory and sparked arguments over slavery.
What Mastery Looks Like: A student connects Texas annexation, competing border claims, and U.S. troop movement to the fighting. They locate land Mexico ceded and explain why adding that land raised questions about slavery.
Common Misconceptions: Some students think the first clash happened on land both countries agreed belonged to the United States. Others think the treaty made Texas a U.S. state or settled the slavery question.
How to Assess It: Exit ticket: Why did fighting begin near the Rio Grande, and how did the peace treaty change both U.S. territory and the slavery debate?

Lesson moves

On a blank 1846 map, draw the Nueces and Rio Grande borders, shade the disputed strip, and mark U.S. troop movement.
Read excerpts from Polk's war message and Lincoln's Spot Resolutions, then write which account of the first clash the map supports.
Sort cards labeled annexation, border claims, troop movement, peace treaty, and slavery debate into causes and effects, then defend one placement.
Compare an 1848 territory map with a current U.S. map, then name three states within land Mexico ceded.

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