Lake Michigan by the Numbers: 22,300 Square Miles of Freshwater

Lake Michigan – 22,300 sq mi (57,800 km²) – is the 3rd largest Great Lake by surface area and the largest freshwater lake entirely within one country (USA).

Vital Stats

• Volume: 4,920 km³ (1,180 cu mi) – 2nd largest (after Superior).
• Max depth: 281 m (923 ft) – Chippewa Basin.
• Avg depth: 85 m (279 ft).
• Shoreline: 2,633 km (1,636 mi) – including islands.
• Retention time: 99 years (slow flush).
• Basin population: 12M+ (Chicago, Milwaukee, Green Bay, Gary).

Unique Geography

• Only Great Lake wholly in US – Others share Canada border.
• Connected to Lake Huron via Straits of Mackinac (hydrologically one lake).
• No major river inflow – Mostly direct precipitation + groundwater.

Economic Engine

• Shipping: 50M+ tonnes/yr (iron ore, coal, grain, cement).
• Fishery: $7B+ (salmon, trout, perch, whitefish).
• Recreation: $20B+ (beaches, boating, sport fishing).
• Water supply: 10M+ people.

Ecological Challenges

• Invasives: Zebra/quagga mussels, round goby, alewife, sea lamprey.
• Nutrient loading – Algal blooms (Green Bay, Saginaw Bay).
• Coastal erosion – High water + no ice cover = wave attack.
• PFAS/Pollution – Industrial legacy (Fox River, Grand Calumet).

Lake Michigan: Inland sea, economic lifeline, ecological battleground—all in one basin.