On or about your person...

[BrianF-Jax]

Is it safe to assume that would include a backpack, bag, or briefcase?

Hypothetically... what if you took public transit, just bought a new knife, (we'll go ahead and say it isn't a common pocket knife, something >4" and scary looking...) and you're on your way home on the bus. It's in your backpack. Could you be arrested for carrying a concealed weapon?

I'd be screwed if I had to take the bus, how would I tote all these guns to the range?

 

[medusaoblongata]

If you just bought a knife and it's in that little plastic baggy in the box in a bag with a receipt from that day, you probably don't have to worry about getting busted for carrying that knife concealed.

I believe that "on or about your person" includes in any bag that you're carrying. I'm pretty sure that it does not include anywhere in your car, if you're in one. If I'm right, then carrying a non-legally-concealable knife in a backpack is illegal, but if you set that backpack down on the passenger seat of your car then it is legal, but if you set that backpack down on the seat on the bus next to you it is illegal, I think.

Funny laws, written by funny people.

 

[Erik W]

"I'm pretty sure that it does not include anywhere in your car, if you're in one."

Nope. Actually, maybe. Check your applicable state laws.

Until you know for sure, assume that the passenger compartment of a vehicle is fair game for law enforcement. (I recommend checking with your local DA's office.)