You’re driving south of Dayton, maybe heading toward Cincinnati, and you see the signs for the "Star City." If you've lived in the Miami Valley for a while, you probably know the answer. But for newcomers or folks just passing through, the question of what county is Miamisburg Ohio in is one that pops up more than you’d think.
It’s in Montgomery County.
There. Simple, right? But honestly, if you stop at the county line, you’re missing the weird, radioactive, and ancient layers of why this specific slice of Ohio is so unique. Miamisburg isn't just a dot on a map in southwestern Ohio; it's a place where 2,000-year-old burial mounds sit just miles away from Cold War nuclear labs.
Why People Get Confused
Geography in this part of the state is kinda messy. You have the Great Miami River winding through everything, and a dozen "Miami" townships, cities, and universities. People often assume Miamisburg might be in Miami County. It makes sense, right?
Nope.
Miami County is actually just to the north, home to places like Troy and Tipp City. Miamisburg sits firmly in the southern belly of Montgomery County. It’s tucked inside Miami Township, which only adds to the name-game confusion. If you’re paying taxes or looking for a marriage license, you’re heading to the courthouse in downtown Dayton, not Troy.
The Montgomery County Connection: Life in the Star City
Being part of Montgomery County means Miamisburg shares a backyard with some heavy hitters. We’re talking about the birthplace of aviation. While Orville and Wilbur Wright were tinkering with bicycles and gliders in Dayton, Miamisburg was carving out its own identity as an industrial hub.
Today, the city has a population of roughly 20,000 people. It’s got that "small-town feel" but with the economic engine of a much larger metro area. In 2026, the local economy is a mix of high-tech and legacy manufacturing. You’ve got places like Avery Dennison and Yaskawa Motoman providing a lot of the local paycheck power.
But it’s not all spreadsheets and factory floors.
The Mound: A Massive Piece of History
You can't talk about Miamisburg without talking about the Mound. It’s literally in the name of the local high school teams (Go Vikings!).
The Miamisburg Mound is this massive, conical earthwork built by the Adena people somewhere between 800 BC and 100 AD. It’s one of the largest of its kind in North America.
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- It stands nearly 70 feet tall.
- There are 116 concrete steps to the top.
- Once you're up there, you can see for miles across the Montgomery County landscape.
It’s a bit surreal to stand on top of a 2,000-year-old grave while looking out at modern suburban rooftops. It reminds you that "what county is Miamisburg Ohio in" is a relatively new question in the grand scheme of things.
The Secret Nuclear History (The Mound Lab)
Here’s the part most travel brochures gloss over: Miamisburg played a massive role in the Cold War.
The Mound Plant was the first permanent site of the Atomic Energy Commission. Started in 1947, this place was top-secret. We’re talking Manhattan Project levels of "don’t ask what we’re doing here." They worked on polonium-210 initiators for atomic bombs and later became a leader in tritium processing.
The lab eventually closed in the 90s, and after a massive environmental cleanup, it’s now the Mound Business Park. It’s a wild example of "swords into plowshares"—turning a nuclear weapons facility into a place where tech startups and green energy companies set up shop.
What to Do While You’re in Town
If you’re visiting Miamisburg to settle a bet about the county or you're looking for a weekend spot, the downtown area is actually pretty legit. It hasn't been swallowed up by generic strip malls yet.
- The Great Miami River Trail: This is a big deal for cyclists. It’s part of the nation's largest paved trail network. You can ride from Miamisburg all the way up through Dayton and beyond.
- Baum Opera House: Built in the late 1800s, this place almost got torn down in the 90s. The community saved it, and now it’s the heartbeat of the local arts scene.
- Local Eats: You’ve got Bullwinkle’s Top Hat Bistro (get the ribs) and Lucky Star Brewery. The vibe downtown is very "park the car and walk."
Practical Info for Residents and Visitors
Since we know Miamisburg is in Montgomery County, here are a few things that actually matter for your day-to-day:
- School District: Most of the city is served by Miamisburg City Schools.
- Neighboring Towns: You’re right next to West Carrollton, Germantown, and Centerville.
- Access: I-75 runs right along the edge of town, making it a 15-minute hop to Dayton or a 45-minute trek to Cincinnati.
The median household income has been climbing lately—hitting over $80,000 according to recent data. It’s becoming a "wealthy" suburb compared to some other parts of the county, but it still keeps its blue-collar roots close to the chest.
Actionable Insights for Your Visit
If you find yourself in this corner of Montgomery County, don’t just drive through.
- Climb the Mound: It’s a workout, but the view of the Miami Valley is the best you’ll get without a drone.
- Check the Calendar: Miamisburg does "Spring Break" and "Rock 'n' Green" festivals that bring in people from all over the county.
- Visit the History Center: Located on Fifth Street, the Miamisburg Historical Society has the real dirt on the "Star City" origins and the nuclear secrets.
Knowing that Miamisburg is in Montgomery County is just the entry point. Whether you’re interested in ancient civilizations, nuclear history, or just a really good craft beer by the river, this town has a weirdly deep story to tell.
Check the Montgomery County Auditor’s site if you need specific property tax data, or hit up the City of Miamisburg’s official portal for trash pickup and local ordinances. For everyone else, just enjoy the drive down Route 25.