Montana: Roosevelt County
> Median age: 30.2 years (state: 39.9 years)
> Population under 18: 33.5% (state: 21.7%)
> Population 65 and over: 11.1% (state: 18.2%)
> Total population: 11,175
> Largest place in county: Wolf Point
Nebraska: Thurston County
> Median age: 27.5 years (state: 36.5 years)
> Population under 18: 35.9% (state: 24.8%)
> Population 65 and over: 11.9% (state: 15.4%)
> Total population: 7,181
> Largest place in county: Pender

Source: jmoor17 / Getty Images
Nevada: Elko County
> Median age: 34.1 years (state: 38.0 years)
> Population under 18: 27.4% (state: 22.9%)
> Population 65 and over: 11.0% (state: 15.4%)
> Total population: 52,297
> Largest place in county: Elko

Source: DenisTangneyJr / Getty Images
New Hampshire: Strafford County
> Median age: 36.9 years (state: 42.9 years)
> Population under 18: 18.7% (state: 19.3%)
> Population 65 and over: 14.6% (state: 17.5%)
> Total population: 129,124
> Largest place in county: Dover

Source: SeanPavonePhoto / Getty Images
New Jersey: Hudson County
> Median age: 35.3 years (state: 39.9 years)
> Population under 18: 20.5% (state: 22.1%)
> Population 65 and over: 11.7% (state: 15.9%)
> Total population: 670,046
> Largest place in county: Jersey City
Sponsored: Find a Qualified Financial Advisor
Finding a qualified financial advisor doesn’t have to be hard. SmartAsset’s free tool matches you with up to 3 fiduciary financial advisors in your area in 5 minutes. Each advisor has been vetted by SmartAsset and is held to a fiduciary standard to act in your best interests. If you’re ready to be matched with local advisors that can help you achieve your financial goals, get started now.