What's Illegal By State Or City (If Significantly Different) 
Alabama: Concealed "Bowie" knives (i.e large fixed blades, even kitchen knives), machetes and knives that look like guns. Totally cool to wear any of those on your hip though.
Alaska: Gravity knives and switchblades. And you're supposed to tell a cop you're carrying a knife if he stops you.
Arizona: Anything goes. Tell a cop if you're carrying one.
Arkansas: Please, carry any sort of knife you'd like.
California: No dirks, daggers, stilettos or ballistic knives. No undetectable (ie non-ferrous or hidden in a cane) knives. You're supposed to carry big knives unconcealed.
Los Angeles: Don't carry knives in plain view. Exposed pocket clips are supposedly fine.
Colorado: Don't conceal anything over 3.5 inches. No ballistic knives.
Connecticut: No automatics or stilettos over 1.5 inches. You can't carry anything over 4 inches.
Delaware: The only knives you can conceal are pocket knives of 3 inches or less.
Florida: If you're going to conceal it, make it 4 inches or less.
Georgia: If it's over 5 inches, you need a weapons permit if you want to conceal it.
Hawaii: No balisongs or switchblades. Don't conceal anything that looks dangerous. Real men fight with their fists anyways.
Idaho: Knives are cool here!
Illinois: No switchblades, throwing knives or ballistic knives.
Chicago: Keep it under 2.5 inches.
Indiana: No ninja stars or pizzas at gay weddings.
Iowa: Pretty much anything goes, but you're not supposed to conceal anything over 5 inches or a dagger or switchblade or can knife.
Kansas: No throwing stars or ballistic knives.
Kentucky: Ain't no knife laws here. Except you're ain't supposed to conceal anything scary lookin'
Louisiana: No switchblades.
Maine: Illegal to carry daggers, stilettos or "knives designed for harming others."
Maryland: You can't conceal a throwing star, dirk, switchblade, gravity knife or bowie.
Massachusetts: The few survivors of the last winter encouraged not to carry switchblades, dirks, stilettos, ballistic knives or ones with knuckle guards as they forage for what meager sustenance remains.
Michigan: Anything goes. Don't conceal stilettos though.
Minnesota: Anything goes except for switchblades, don't you know.
Mississippi: You can't own anything scary looking if you're a minor or a convicted felon. And no one's supposed to conceal that scary stuff either.
Missourah: No switchblades.
Montana: Don't conceal anything over 4 inches.
Nebraska: It's illegal for a felon to own a knife, which must make cooking interesting. Anyone else can own and carry whatever they want.
Nevada: No belt buckle knives, which are apparently a thing. Don't try and conceal anything scary.
New Hampshire: Don't tread on me.
New Jersey: Tony and Vinny can own and carry whatever they want except a switchblade.
New Mexico: No switchblades or butterfly knives.
New York: You can't own a knife unless you're a US Citizen. A law currently being violated at every restaurant in the state. And no one's supposed to have anything scary like a switchblade, throwing star or sword.
New York City: No gravity knives. The cops will make this mean anything if they want to. No knives over 4 inches.
North Carolina: Nothing that shoots its blades. Don't conceal carry a butcher knife, a bowie knife or anything scary.
North Dakota: No concealing your machete, switchblade or anything else that's over 5 inches.
Ohio: Anything goes, just don't be a child playing with a toy gun in a park.
Oklahoma: You can't carry anything scary, concealed or open.
Oregon: Believes it violates your 2nd amendment rights to tell you what knives you can have or carry.
Pennsylvania: It's illegal to own a dagger, automatic knife or sword cane. You can't open or conceal anything scary, including hunting knives. I bet a lot of people break that last law pretty constantly.
Rhode Island: Don't conceal anything over 3 inches. And the usual no scary stuff.
South Carolina: Own and carry anything you want, any way you want.
South Dakota: Not sure there's actually laws of any kind here, but you're definitely cool with whatever knife you want.
Tennessee: You can't carry anything over 4 inches.
Texas: No gravity knives.
Utah: Anything goes unless you've been convicted of a variety of loose criminal charges including delinquency, then no knives for you.
Vermont: No switchblades, if they're over 3 inches.
Virginia: It is legal to own any type of knife in Virginia, it is illegal to conceal anything scary looking.
Washington: No switchblades.
West Virginia: No concealing anything scary looking.
Wisconsin: Don't conceal anything scary looking.
Wyoming: Don't conceal anything scary looking.
