If the breaker would reset if there is no outlet connected, but won't if one is wired, then either the outlet is defective or it's wired wrong. If you have a circuit tester, then I would turn off the breaker, and remove the receptacle. Check which screw each wire is connected to.

There are lots of possibilities with something like this, but here are just a few possible scenarios.

1. The electricians who wired your house weren't too careful with keeping the NM cable away from the face of the studs, and the drywall hangers managed to drive a screw or nail partway into a cable. Nobody noticed at the time, but now that screw or nail has moved just a little. Maybe the house settled a bit, or you had an earth tremor, or a big truck drove by, or just simple expansion and contraction from heating and cooling moved it. In any case, it's now touching both a hot wire and a neutral or ground. That's a short circuit.

2. A bare ground wire got too close to a hot terminal in a box somewhere, and again it's shifted just enough to cause a short circuit.

3. If your area had adopted the 2008 NEC by the time your house was built, it will have AFCI (arc fault circuit interrupter) breakers for most living spaces. A loose connection in a junction box, this one or possibly even one on the other side of the wall, could arc under load and cause its AFCI breaker to open.

Another possibility, less likely if you're sure you're hearing a pop, is that neutral and ground wires have come into contact and a GFI breaker is tripping.

I'd start by first determining whether the problem is a short circuit or a loose connection. Get a battery powered continuity tester at the hardware store. If it has only one clip lead, buy an extra clip lead, too.

You can also use the ohmmeter function of a DMM (digital mutlimeter), but for something like this a continuity tester that produces a tone is easier to use and more accurate.

Shut off the main breaker, then remove the black or red wire from the breaker for this circuit. Clip the tester's probe to the black wire, and connect the tester's clip to the neutral bar in your panel. You can also just clip it onto any bare ground wire.

Make sure the main breaker is off for all this!

If the tester shows continuity, you have a short circuit. If it doesn't, and you have an AFCI breaker on this circuit, it's more likely to be a loose connection.

There are outlier cases, but if you have a loose connection, it'll almost certainly be in a junction box somewhere. Open every box on the circuit and check for loose terminal screws on devices and loose wirenuts. In many cases the culprit will jump right out at you, because it'll look discolored or charred from excessive heating.

If you have a short circuit, that might also be in a box. Open 'em up and look for evidence of arcing, such as soot deposits.

If you don't find it in a box, then you'll have to isolate each section of the circuit by disconnecting everything in every box. Make sure everything is disconnected. An appliance left plugged in can fool you.

Once you've isolated all circuit sections, use your continuity tester on the cable at each box to look for continuity (tone or light) between hot (black/red) and neutral (white/light grey), and also between hot and ground (bare or green) wires.

Be aware that in a switch loop, a white or light grey wire can be a hot wire. A "promoted" white or light grey wire is supposed to be re-identified with tape or paint in a color other than grey, white, or green, but my experience is that this rule is more often honored in the breach.

When you find continuity between wires that shouldn't have it, that's the defective section of the circuit. Fixing it may require drywall surgery. If you're lucky, you might be able to abandon the bum section in place, and fish a new cable. I've heard of guys who can fish through junction box knockouts, but I've always had to tear out the boxes in a case like that. A fine tooth jigsaw or pocket hacksaw to cut the nails probably holding the boxes to the studs is handy for this.

If all this sounds too complex, then it's probably time to call in a pro.

Good luck! Let us know what you find.

"If the breaker would reset if there is no outlet connected, but won't if
one is wired, then either the outlet is defective or it's wired wrong."

OR the electrical fault is in any of the boxes downstream of the box you disconnected. Anything bad in the downstream string from the outlet would be removed from the circuit if you disconnect the upstream outlet and thus allow the breaker to reset.