The sound you don't want to hear at midnight
If you're reading this, there's a decent chance water is moving somewhere it shouldn't be, or you just read a story about someone whose basement flooded while they fumbled around looking for a valve they'd never used. That's the normal way people in Nixa learn about their main shutoff: after the fact, with wet socks.
Around here, the usual culprits are a supply line that finally gave out after fifteen or twenty years, a washing machine hose that split, or a pipe that froze and cracked during one of our hard cold snaps and then let go the moment things thawed. In every one of those cases, the first thing that matters isn't the leak itself. It's how fast you can stop the water.
Why Nixa homes make this trickier than it should be
Nixa grew fast, and the housing stock reflects that. You've got older homes near downtown with galvanized or early copper plumbing, newer builds out toward the edges of town with PEX, and everything in between from the building boom of the 2000s and 2010s. Shutoff valve location and type often depends on which era your house came from, and whether the original contractor bothered to make it easy to find.
Add to that the fact that a lot of homes here sit on slab foundations rather than full basements, especially in the newer subdivisions. On a slab home, the main shutoff is often outside, near where the water line enters the house, sometimes tucked against the foundation under a bush or behind an AC unit. In older homes with crawl spaces, it might be inside, near the water heater, or it might be the valve on the meter pit at the street. There's no single answer for Nixa, which is exactly why you need to go find yours instead of assuming it matches your neighbor's.
More on this from Redeemed HVAC in Nixa.
What to actually go check this weekend
Start inside. Walk to wherever your water heater or main plumbing stack is, usually a utility room, garage wall, or crawl space access. Look for a valve, either a round wheel-style or a lever-style ball valve, sitting on the pipe before it branches off to the rest of the house.
If you don't find one inside, go outside and look near the front of the house, close to where you'd guess the water line comes in from the street. It may be a small valve box flush with the ground, sometimes with a metal or plastic lid you'd need a flathead screwdriver or a meter key to lift.
Once you find it, turn it. Not all the way through a full shutdown test if you're nervous, but enough to feel whether it moves freely or whether it's seized up with mineral deposits and age, which happens a lot with valves that haven't been touched in ten or fifteen years. A valve that won't turn is not a shutoff, it's a decoration.
What the seasons do to this problem
Our winters aren't Minnesota winters, but they're enough. A cold snap that pushes overnight temperatures into the single digits for a few days, which happens most years, is exactly when pipes in unheated crawl spaces or exterior walls are most likely to freeze and split. If that happens at 2 a.m. during an ice storm, you do not want to be learning where your shutoff is for the first time while water is running down the hallway.
Summer brings its own version of the same risk. Heat and dry spells can shift and crack slab foundations slightly, which stresses the pipes running through or under them. It's less dramatic than a frozen pipe bursting, but a slow slab leak can run for weeks before anyone notices, and knowing where the shutoff is means you can kill the water the moment you spot a damp patch on the carpet or a spike in your water bill.
When it's time to call someone
Finding and testing your shutoff is a homeowner job. So is knowing the rough path of your main line and keeping the area around the valve clear of landscaping, mulch, or stored junk so you're not digging through brush in the dark.
Where it stops being a homeowner job is the moment the valve won't close all the way, drips after you've shut it, or you can't find one anywhere on the property. At that point you're not dealing with a convenience issue, you're dealing with a house that has no reliable way to stop water in an emergency, and that's worth getting fixed before you need it rather than during the flood. Same goes for any actual leak once you've got the water stopped: a shutoff buys you time, it doesn't fix a cracked pipe or a failed water heater, and trying to solve that part yourself at midnight is how a bad night turns into a bad month.