Crack the Case: History's Toughest Mysteries

Essential Question

How do we develop and support theories about historical events using primary and secondary research sources?


This project will guide students though a project-based inquiry into one of history’s famous cold cases. Students will choose a mystery to investigate, seek out and analyze both primary and secondary sources, develop a theory as to what happened in the mysterious historical event, and support their theory with evidence from their research.  In the end, students will present a “Case File” on their mystery, including a final report of their research findings and copies of the relevant source material.

Suggested Grade Level

This lesson is written for grades 9-12, but can be adapted for use in grades 6-8, as well. For middle school grades, reduce the number of cold cases students can choose and pre-screen the primary and secondary sources to ensure students will more readily find helpful evidence.


Estimated Time Required
3-5 class periods

Related Episodes: History Detectives Special Investigations

In Season 11 of History Detectives, the detectives devote the entire hour to investigating four of history’s unsolved mysteries: the tragedy of the Sultana steamboat, the Austin servant girl murders, the disappearance of Glenn Miller in World War II, and the killing of Jimmy Hoffa. These episodes show the History Detectives following a string of clues, from primary sources uncovered in archives to the opinions of current-day experts, in an effort to finally crack open one of history’s enduring cold cases.

Set Up

  • Make photocopies of the “Cracking History’s Cold Cases: A Research Project” reproducible.
  • Make copies of the “Your Investigation, One Clue at a Time” Graphic Organizers. These graphic organizers are designed to allow students to use as many as they need in conducting their organizer. Make enough copies for students to have at least four copies each.
  • Bookmark the sources for this project on students laptops or tablets, or in student computer lab


Ask students to discuss in small groups or do a free-write in response to the question: What is one of the great unsolved mysteries of history? Why do you think people remain so interested in this mystery?

Then lead a whole-class discussion about these mysteries. Possible responses include: the Lost Colony of Roanoke, the Great Chicago Fire, the crash of Amelia Earhart, the kidnapping of the Lindbergh baby, the death of Jimmy Hoffa, Lizzie’s Borden’s alleged murder of her parents, or even, the recent loss of Malaysian Airlines Flight 370. Ask students why they personally find the mystery interesting and what makes it worthy of investigation. Guide students to understand that even if the reason why people remain interested is their base curiosity about the cruelty of people (i.e., people’s continuing fascination with Lizzie Borden and her axe) or great tragedy (i.e., the Chicago Fire), studying these mysteries can yield insights into the historical time period that are more valuable than the titillation the mystery provides.


Explain to the class that they will be investigating one of the history’s unsolved “cold cases.” In their research, they will examine both primary and secondary sources to arrive at what they consider the best theory as to what actually happened.

Before beginning the investigation, activate prior knowledge about historical research. Ask students, “What is a primary source? What is a secondary source?” (primary sources were written or created at the same time as the event in question; secondary sources are at least one step removed from the event in question and usually present some sort of interpretation or analysis of primary source and/or secondary source materials.)

Pass out copies of the “Cracking History’s Cold Cases: A Research Project” reproducible and at least one copy of the “Your Investigation, One Clue at a Time” graphic organizer. Read the task aloud to students:

History is filled with unsolved mysteries. Your task in this research project is to choose one of those mysteries and present a plausible theory to explain it. You will research a variety of primary and secondary sources to uncover possible theories and the clues that support them. After you conclude your research, you will create a “Case File” that includes: background on the mystery, the most plausible theory, and a collection of annotated evidence that backs up that theory.

Give students a brief overview of the four cold cases from American history they may investigate. (Please note, cold cases are listed in order from most accessible to most complicated. You may choose to assign students their cold case based on complexity level or allow students to choose their own.)

  • The Great Chicago Fire:  A fire raged through the city of Chicago from October 8 through October 10, 1871, killing hundreds. The traditional story has it that a cow owned by the O’Leary family kicked over a lantern in its barn, starting a fire that spread to over three square miles. But was it really Mrs. O’Leary’s cow that started the fire?
  • The Disappearance of Amelia Earhart: Amelia Earhart was the first woman to fly solo across the Atlantic Ocean in 1932. On June 1, 1937, Earhart and her flight navigator Fred Noonan left Miami, Florida, on the first leg of a journey that would make her the first woman to fly around the world. On July 2, Earhart and Noonan took off from Howland Island in the Pacific Ocean and simply disappeared. Did they crash? And, if so, where?
  • The Lost Colony of Roanoke: The Colony of Roanoke was settled in 1587 on an island in present-day North Carolina. The colony’s governor, John White, sailed home to England for supplies. When he returned three years later—delayed by the Spanish-American War—the colony had disappeared entirely. The only evidence left behind was the word “Croatoan” carved into a wooden post. What happened to those settlers?
  • The Disappearance of Glenn Miller in World War II: Glenn Miller was a famous big band leader in the 1930s and ‘40s. During World War II, he and his big band were important ambassadors for American values, playing swing music throughout Europe and broadcasting their music over the radio throughout both Allied and Axis countries. But on December 15, 1944, Glenn Miller boarded a plane to fly from Britain across the English Channel to Paris. He was never seen again. Did his plane sink in the English Channel? Was it friendly fire? What ever did happen to the famous bandleader?

Instruct students that they will use the “Your Investigation, One Clue at a Time” graphic organizers in order to Think Like a Historian while conducting their research project.  The graphic organizer will take them through the following steps for each clue and/or source they investigate:

  • What question do you want to answer?
  • Source Name and Description: Title and notes about what type of document they are investigating (letter, article, photograph, interview, etc.)
  • Sourcing: Who made this source? Where did it come from?
  • Contextualizing: Imagine the setting surrounding this source: How was the world that made this source different than our own?
  • Corroborating: What do other sources say about the information in this document? Do they agree or disagree with what this document says?
  • Close Reading: What does the document say? Is it biased? What is the tone?
  • Further Investigation: Notes about what questions this source raises and/or doesn’t sufficiently answer.

Allow students time in class to begin their research using the links provided. Circulate the room and assist students as necessary.

Students can complete their research in class or as an independent project.

At the conclusion of their research, have students create a Case File that include the following elements:

  • Background on the Historical Event
  • The Most Plausible Theory
  • At least three pieces of evidence that support that theory
  • An explanation of each piece of evidence you present
  • Explanation of one alternate theory and your reasons for discarding it
  • Why this investigation was a worthwhile endeavor


Have students present their projects to class as oral presentations or a gallery walk. Encourage students to comment on and challenge one another’s conclusions and to defend their own conclusions by citing the evidence and explaining its credibility. 

More on History Detectives

You may also wish to have students research one of the cold cases in the following episodes of HDSI:

Episode: Who Killed Jimmy Hoffa?

Episode: Texas Servant Girl Murders

Episode: Tokyo Rose


This lesson aligns with these National History Standards, US History Content Standards and Common Core State Standards.