Your description is a little confusing (receptacles have no "load" side), but what you encountered is a multiwire circuit and is quite common. Two requirements that seem to be missing in your case are that the neutrals must be continuous (wire nutted and pigtailed to the receptacle) and if both hots land on the same yoke (receptacle), the breaker handles must be tied together.

Yes, I know that non-GFCI outlets don't have a "line" and "load" but I am just borrowing terms from them. The white neutral wires were simply joined at the receptacle, and not wire nutted and pigtailed as you mention. I know this standard from reading "wiring simplified" which was recommended in another thread. (thanks!).

What you mean by breaker handles tied, does this mean that the panel should be labelled that breaker#3 and breaker#7 should be turned off when working on any device/outlet/switch on this circuit(s)?

For some reason, the seller did his own labelling scheme and did not follow the diagram that is on the ITE Pushmatic panel, but needlesstosay, breaker #3 is on the left hand side, and breaker#7 is on the right, a few rows down from #3. I have kept his weird labelling scheme for now.

Jay

I am just borrowing terms from them

Please don't; it confuses things when you use nonstandard terms.

What you mean by breaker handles tied

That means the handles are mechanically joined, so they can't operate separately. If one trips, the other opens. If one is shut off, the other is too. Thus, they work like a double-pole breaker, which may also be used.

I have kept his weird labelling scheme for now.

What you did was OK except that the ground should be connected to the box (if it's metallic).

You also could have fitted a properly sized double pole breaker to the panel, and connected the hots to it. You'd also have needed to pigtail the neutrals so removing one of the recepts wouldn't break it.

Am I going to find other surprises in my wiring

Probably. Almost every house I've ever lived in has had some (usually unpleasant) wiring surprises. Sometimes it's pros, but I suspect that more often it's DIYs. DIY wiring has been around for a long time, and too many DIYers don't learn code or proper techniques before plowing ahead.

One more thing to look at on 3 wire + ground circuits. If two separate breakers are used it is very important to make sure that they are on different busses in your breaker box. If they are on the same bus then the currents will ADD in the neutral wire and you can overload the neutral without tripping a breaker. That can ruin a wire and cause a fire.

If you put the breakers on different busses in the box then the neutral current will cancel and only the unbalanced current will run in the neutral.

In my box adjacent tabs on one side are on opposite busses, so a double pole breaker solves this problem.

Of course you will have 240V in any box with both a red and a black, I don't care for that either, 240 can hurt you, so now I just use 12/2 for everything and don't worry about the wasted wire and slightly lower electrical efficiency. I use my 12/3 for 3-way switches and wiring smoke detectors together. It will also make it easier to put in AFCI breakers if that becomes a requirement.

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[i]That means the handles are mechanically joined, so they can't operate separately. If one trips, the other opens. If one is shut off, the other is too. Thus, they work like a double-pole breaker, which may also be used.[/i]
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OK, this was definitely not the case... But I've split those circuits off now anyway so it is moot now.

What should I call the hot/neutral coming from downstream? Is there a technical term for it to separate it from the hot/neutral coming from the circuit panel?

My first home, so I'm new to much of this electrical stuff other than high school physics...

Jay

I never really thought about it for anything but a GFCI outlet but LINE is a source of voltage and LOAD is anything on a circuit that draws current. So if you have an outlet with wires coming in from the breaker those wires would be from LINE and if you have wires going out to another outlet with something plugged into it those wires would be going to LOAD. So it seems reasonable to call them line side and load side.

But if that offends then I guess you could use upstream and downstream, of course then you will annoy the river boat pilots....

Maybe I should start a poll:

How many river boat pilots on this forum?

How many people who are offended that I use GFCI terms on regular non-GFCI receptacles?

:-)

As a kayaker (who kayaks rivers too), I am not offended by the upstream/downstream even on tidal rivers. It is generally understood when talking about upstream/downstream on say the Hudson River even though it's tidal til about Albany, NY.

Jay

"What should I call the hot/neutral coming from downstream? Is there a technical term for it to separate it from the hot/neutral coming from the circuit panel?"

I use the highly technical terms of "power in" and "power out".