Detective Briefing Slides
TOP SECRET
CLASSIFIED
Prairie Detective Agency
Mission: Illinois History Cold Case
IAR PREP: INFORMATIONAL TEXT EDITION
The Mission Briefing
Your Task:
Analyze the evidence (text) about the ancient city of Cahokia. Solve 3 Clues to close the case.
Required Skills:
- Finding the Main Idea
- Part A & Part B Evidence Pairs
- Vocabulary Decoding
Form Your Teams
Each squad needs a Lead Investigator (captain), a Scribe, and an Evidence Specialist.
FILE #400: THE LOST CITY OF CAHOKIA
Long before Chicago was a city, a massive metropolis stood in what is now southern Illinois. Known as Cahokia, this city was the center of the Mississippian culture between 700 and 1350 CE. At its peak, nearly 20,000 people lived there, making it larger than London at the same time!
The most striking feature of Cahokia is its massive earthwork mounds. These weren't just piles of dirt; they were sophisticated structures. The largest, Monks Mound, stands 100 feet tall and covers 14 acres. Building it required carrying over 20 million baskets of soil by hand. This suggests the Cahokians had a highly organized society with powerful leaders.
Cahokia was also a bustling trade hub. Archaeologists have found copper from Lake Superior, sea shells from the Gulf of Mexico, and mica from the Appalachian Mountains. This proves that Cahokia was the heart of a vast network that connected people across North America.
Around 1200 CE, the population of Cahokia began to decline. By 1350, the city was mostly abandoned. What happened to this great civilization? Detectives of history have several theories. Some suggest that environmental changes, such as floods or a cooling climate, made it difficult to grow enough corn to feed everyone. Others believe that internal conflict or disease led to the city's unraveling.
While the people left, their legacy remained. Today, the Cahokia Mounds State Historic Site is a UNESCO World Heritage site. It serves as a reminder that Illinois was a center of innovation and community centuries before modern maps were ever drawn.
"Cahokia represents the most sophisticated prehistoric native civilization north of Mexico." — Agency Chief Report
CLUE #1
The Core Claim
Part A
What is the main idea of the section describing the mounds of Cahokia?
- A. The mounds were built to hide treasure.
- B. The mounds show that Cahokians were organized and skilled.
- C. Monks Mound is the only mound in Illinois.
- D. Dirt was the only resource available to the builders.
Part B
Which sentence from the text best supports the answer to Part A?
- A. "These weren't just piles of dirt..."
- B. "Building it required carrying over 20 million baskets of soil..."
- C. "...covers 14 acres."
- D. "The largest, Monks Mound, stands 100 feet tall."
CLUE #2
Word Detective
"Others believe that internal conflict or disease led to the city's unraveling."
Based on the sentence above, what does the word "unraveling" most likely mean?
A. Growing larger and more popular.
B. Falling apart or coming to an end.
C. Moving to a new location.
D. Discovering a new secret.
CLUE #3
The Trade Trail
Which detail supports the claim that Cahokia was a "bustling trade hub"?
A Nearly 20,000 people lived there at its peak.
B Archaeologists found copper from Lake Superior and shells from the Gulf of Mexico.
C The city was mostly abandoned by the year 1350 CE.
D Cahokia was larger than the city of London at the same time.
CASE FILED
All evidence has been gathered. It's time to verify your findings with the Agency Chief. Do your claims hold up under scrutiny?
Awaiting Verification...
Case Evidence Report Worksheet
Case Evidence Report
Prairie Detective Agency // IAR Mission #400
Detective:
Date:
Analyze the text in the slides. For Part A/B pairs, you must select the correct answer for both parts to earn the Evidence Badge.
1
Clue #1: The Core Claim
Part A: The Main Idea
A
B
C
D
Part B: Text Evidence
A
B
C
D
2
Clue #2: Word Detective
Select the meaning of "unraveling":
A
B
C
D
3
Clue #3: The Trade Trail
Select the best evidence from the list:
A
B
C
D
Lead Detective Summary
Write a 2-3 sentence summary of Cahokia's legacy based on the evidence:
Case Filed
Agency Chief Manual Key
Agency Chief's Manual
Master Key & Facilitation Guide
Agency Roles
The Agency Chief (Teacher)
You are the overall supervisor. You control the slides and verify team evidence files before allowing squads to move to the next clue.
Lead Investigators (Students)
Each team picks one Lead Investigator to be the group captain. They are responsible for bringing the Case Report to you for verification.
Gameplay Instructions
- Verification Checks: After each clue slide, teams should consult. Once they decide, the squad's Lead Investigator brings the worksheet to you for a "Chief's Stamp" (or sticker).
- Point System: For Part A/B pairs, only award the stamp if both parts are correct—this reinforces the IAR's evidence-based scoring.
Master Case Key
CLUE #1: The Core Claim (IAR Standard: RI.4.2)
EBSR PAIR
Part A (Main Idea)
B. The mounds show that Cahokians were organized and skilled.
Part B (Evidence)
B. "Building it required carrying over 20 million baskets of soil..."
CLUE #2: Word Detective (IAR Standard: RI.4.4)
Correct Interpretation:
B. Falling apart or coming to an end.
CLUE #3: The Trade Trail (IAR Standard: RI.4.1)
Supporting Detail:
B. Archaeologists found copper from Lake Superior and shells from the Gulf of Mexico.
Final Summary Rubric
1 POINT
States one simple fact without explaining significance.
2 POINTS
Mentions Cahokia as an ancient metropolis with a lasting physical legacy.
3 POINTS
Identifies Cahokia as a sophisticated, influential society that remains a center of innovation.
