Grade 8 · US History · §113.20 · Problem-Based Learning
Crossing the Continent, 1845 — How Far Should the Nation Go?
A Problem-Based Learning unit. Students step into the expansion debate of the 1840s, take on a stakeholder's point of view, and work a real, ill-structured question — building from surface to deep to transfer learning. The teacher is a guide, not the answer key.
Driving question: It is 1845, and "Manifest Destiny" is in the air. Many Americans believe the United States should stretch from coast to coast. But expanding west means annexing Texas, risking war with Mexico, moving onto lands where Native nations already live, and reopening the bitter question of whether new territories will allow slavery. As citizens and leaders, how far and how should the nation expand?
The three-phase path (do them in order)
Problem-solving is a transfer move — it only works once students have knowledge to reason with. So the problem in Phase 3 is deliberately gated behind Phases 1 and 2.
⛔ Gate: don't open the Phase 3 problem until students have finished the surface and deep activities. Meeting the problem too early turns inquiry into guessing.
Big idea & objectives
Big idea: Westward expansion promised opportunity for some but came at great cost to others — and it forced the nation toward the sectional crisis over slavery. It was a decision with winners, losers, and deep moral stakes.
Know: what Manifest Destiny meant, how the U.S. gained Texas, the Oregon Country, and the Mexican Cession, and how the geography of the continent shaped where and how people expanded.
Understand: the same expansion looked different from each stakeholder's point of view — and every acre gained reopened the question of slavery that would divide the nation.
Do: run the problem-solving process end to end — define a problem, gather information, weigh options, choose and defend a solution, and evaluate it (§113.20(c)(31)(B)).
Standards this unit is aligned to (§113.20)
TEKS SE
Where it lives in the unit
(c)(6)
Westward expansion & its political, economic, and social effects — Surface jigsaw, Deep map, Transfer brief
(c)(7)
Factors leading to the growth of sectionalism — Deep concept map, Transfer debrief
(c)(10) · (c)(11)
Location & physical characteristics of the U.S. and how geography shaped expansion — Surface map/data work
(c)(12)
Why sections developed different economic systems — Deep concept map
(c)(21) · (c)(23)
Different points of view; relationships among people from various backgrounds — Deep argument, Transfer roles & debrief
(c)(29)(A–H)
Source analysis, points of view, claim + evidence — Deep & Transfer
(c)(31)(B)
The problem-solving process — the entire Transfer phase
Teacher prep & materials
Print the facilitator guide (teacher moves, map of possibilities, stakeholder role cards, debrief prompts) and the assessment pack (rubric + individual-in-group).
Chart paper or a projected space for three shared columns: Hunches · Know · Need-to-Know (the KWHL chart).
Vetted primary sources for investigation (district-approved). Suggested public-domain sources — the Treaty of Guadalupe Hidalgo, the Oregon Treaty, the Wilmot Proviso, overland-trail records — are listed in the facilitator guide.
No logins, no accounts — every page runs in the browser. Student writing and products live on paper or in tools your district already vets.
Aligned to (not reproduced from) 19 TAC Ch.113 §113.20; effect sizes from Visible Learning MetaX. This scenario dramatizes the real debates over westward expansion in the 1840s.