Worksheet Grade 9 Social Studies & Civics

The 1873 Cravenhurst Outbreak: Mapping a Water Supply

A grade 9 worksheet in which students turn ward case counts from a fictional 1873 outbreak into rates and judge what the health officer's map revealed.

Grade: Grade 9
Subject: Social Studies & Civics
Material: Worksheet
Time: 50 min
Prep: No prep
Materials: Calculator

Standards

HSN-Q.A.1 Common Core Math

Use units as a way to understand problems and to guide the solution of multi-step problems; choose and interpret units consistently in formulas; choose and interpret the scale and the origin in graphs and data displays.

How this material aligns: Items 1 through 11 require students to interpret the unit of cases per 100 households and to hold it consistent across four wards, two combined groups, and a ratio.

All materials for HSN-Q.A.1 →

D2.Geo.2.9-12 C3 Framework

Use maps, satellite images, photographs, and other representations to explain relationships between the locations of places and regions and their political, cultural, and economic dynamics.

How this material aligns: Item 13 asks students to read the ward map shaded by case rate and explain how the location of the two water sources shaped where illness concentrated.

All materials for D2.Geo.2.9-12 →

D2.Civ.14.9-12 C3 Framework

Analyze historical, contemporary, and emerging means of changing societies, promoting the common good, and protecting rights.

How this material aligns: Items 14 and 15 ask students to analyze how nineteenth-century sanitary reformers changed water provision to protect health and the common good.

All materials for D2.Civ.14.9-12 →

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This material is in the public domain (CC0) and may be copied, edited, and shared freely, without attribution. Updated 2026-09-04.

Objectives

Students will convert ward case counts into rates per 100 households and compare them.
Students will explain what a shaded ward map shows that a table of raw counts does not.
Students will evaluate three responses a council could take to a waterborne outbreak.

Vocabulary

Key words: ward, intake, case rate, sanitary reform, municipal ownership

Teacher overview

Before a laboratory test could identify the organism in a water sample, city health officers found contaminated supplies by mapping who fell ill and asking what those households drank. This worksheet builds a fictional case of that kind, the town of Cravenhurst in 1873, and has students do the arithmetic and the map reading that such an investigation required. The misconception to correct at the start is that a map of case counts shows where disease is worst; raw counts mostly follow where people live, so a ward with many households can look dangerous when it is not. Students see this directly here, because the ward with the highest count is not the ward with the highest rate.

The 1873 Cravenhurst Outbreak: Mapping a Water Supply — Grade 9 Social Studies & Civics

Name: ____________________________ Date: ______________

Student Worksheet

The town of Cravenhurst, its wards, its two water sources, and every figure below are fictional. They are written for this worksheet and modeled on the way nineteenth-century American towns investigated illness spread by water.

In the summer of 1873, many households in Cravenhurst fell ill with a fever and severe stomach illness. The town health officer recorded each case by ward. Two systems supplied the town. The private Cravenhurst Water Company drew from an intake on Thimbleby Creek, downstream of the town's mills and slaughter yards. The Overhill Spring line carried water from a fenced spring on the ridge above town. Each ward was served by one system or the other, never both.

Ward	Households	Water source	Cases recorded
North	400	Thimbleby Creek intake	100
Mill	200	Thimbleby Creek intake	56
East	500	Overhill Spring line	15
South	300	Overhill Spring line	6

The health officer drew a ward map and shaded each ward by its case rate, using four bands: under 5, 5 to 14.9, 15 to 24.9, and 25 or higher cases per 100 households.

Find the case rate for North Ward in cases per 100 households.
Find the case rate for Mill Ward in cases per 100 households.
Find the case rate for East Ward in cases per 100 households.
Find the case rate for South Ward in cases per 100 households.
How many households in all were served by the Thimbleby Creek intake?
How many cases in all occurred in the wards served by the creek intake?
Find the case rate for the creek-served wards together, in cases per 100 households.
How many households in all were served by the Overhill Spring line?
How many cases in all occurred in the wards served by the spring line?
Find the case rate for the spring-served wards together, in cases per 100 households. Round to the nearest tenth.
How many times higher was the creek-served rate than the spring-served rate? Use your answers to items 7 and 10.
Nine of East Ward's 15 cases were boarders at one house. All nine worked in the mill district and drank from a creek-fed standpipe at work. Explain why this detail makes the conclusion about the water source stronger, not weaker.
North Ward had the highest case count of any ward, but not the highest rate. Using your answers to items 1 and 2, explain what the shaded map showed the council that the count column alone did not.
The council debated three responses: move the company intake upstream of the mills, extend the Overhill Spring line to every ward, or post notices telling households to boil water. Rank the three from most to least likely to reduce cases in the next outbreak, and defend your first choice.
Sanitary reformers in this period argued that a safe water supply was a public responsibility rather than a private purchase. Using the Cravenhurst data, explain one reason the private water company might not have moved its intake on its own.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key

Answer: 25.0 cases per 100 households.
Divide 100 cases by 400 households to get 0.25, then multiply by 100.
Answer: 28.0 cases per 100 households.
Divide 56 cases by 200 households to get 0.28, then multiply by 100.
Answer: 3.0 cases per 100 households.
Divide 15 cases by 500 households to get 0.03, then multiply by 100.
Answer: 2.0 cases per 100 households.
Divide 6 cases by 300 households to get 0.02, then multiply by 100.
Answer: 600 households.
Add North Ward's 400 households to Mill Ward's 200 households.
Answer: 156 cases.
Add North Ward's 100 cases to Mill Ward's 56 cases.
Answer: 26.0 cases per 100 households.
Divide 156 cases by 600 households to get 0.26, then multiply by 100.
Answer: 800 households.
Add East Ward's 500 households to South Ward's 300 households.
Answer: 21 cases.
Add East Ward's 15 cases to South Ward's 6 cases.
Answer: 2.6 cases per 100 households.
Divide 21 cases by 800 households to get 0.02625, then multiply by 100, which gives 2.625 and rounds to 2.6.
Answer: 10.0 times
Divide 26.0 by 2.6. Students who use the unrounded 2.625 will get 9.9, which should be accepted with the work shown.
Answer: The nine boarders lived in a spring-served ward but drank creek water at work, so they belong with the creek group rather than the spring group. Their illness follows the water they actually drank rather than the address where they slept. Removing them from East Ward would push the spring-served rate lower still and widen the gap in item 11, so the exception points the same direction as the rest of the fictional data.
Answer: North Ward recorded 100 cases and Mill Ward recorded 56, so the count column made North Ward look like the center of the outbreak. The rates reverse that: Mill Ward stood at 28.0 cases per 100 households against North Ward's 25.0, because Mill Ward held half as many households. Shading the map by rate put both creek-served wards in the top band and both spring-served wards in the lowest band, which showed the council a boundary that followed the pipes rather than a single hot spot.
Answer: Accept any defended ranking that treats moving the intake or extending the spring line as more durable than a boil notice. A strong answer puts extending the spring line or moving the intake first, because both remove the contaminated supply for everyone at once, while a boil notice depends on every household reading it, believing it, and having fuel to heat water every day. A strong answer also notes that the notice is the only option available within a week, so a council might use it while building one of the other two.
Answer: Moving the intake would cost the company money it could not recover from customers who were already paying their rate, and the households falling ill were not the company's only customers or its most powerful ones. The company answered to its owners rather than to voters, so residents in the fictional Mill Ward had no vote that could reach it. This is the argument sanitary reformers used for municipal ownership: a public system can be made to spend on prevention because the people bearing the risk elect the people who set the budget. Accept other well-supported reasons.

Differentiation

Support

Give students the first rate calculation worked out in full, with the words "cases," "households," and "per 100" labeled on each part of the fraction, before they begin item 1. Provide a printed outline map of the four fictional wards with the four shading bands already drawn in the key, so students shade rather than construct the scale.

Extension

Ask students to test whether the fictional outbreak pattern would still be visible if the health officer had recorded cases by street rather than by ward, and to write two sentences on what a smaller unit would gain and what it would lose. Students may also recompute the spring-served rate with the nine boarders reassigned to the creek group and state how much the ratio in item 11 changes.

ELL supports

Pre-teach "ward," "intake," "case rate," and "standpipe" with a labeled sketch of the fictional town showing the creek, the mills, the ridge spring, and the four wards. Provide sentence frames for items 12 through 15: "This detail is stronger evidence because ___," "The map showed ___ that the counts did not," and "The company might not act because ___."

Extensions

Students compare the fictional Cravenhurst response with how their own city or town first built a public water supply, using only the utility's published history page or the local library's local-history summary, and note in one paragraph whether the system began as a private company or a municipal department. A second option is to write the half-page report the fictional health officer would read to the council, stating the two rates, the ratio, and one recommended action.