what’s the significance of 911, why isn’t it some other number?
I’ll guess. At one time, area codes had a 1 in the middle position, but prefixes didn’t. 911 wasn’t an area code or a prefix, and the second “1” meant that a person didn’t have to remember another number. In England the emergency number is 999.
All of the numbers ending in -11 were left out of the pool of prefixes (and, later, area codes) for use by the phone companies. The reason is that, back in the days of rotary-dial phones, information theory required that the numbers requiring the fewest “clicks” should be given to the highest-use functions. So the three-digit “-11” numbers were used for functions like emergency services (911), information (411), etc. (This is the same reason, BTW, that when area codes were initially assigned, the highest-population areas, which were most likely to be called, got codes like 212, 202, 312, 301, etc.)
As to why it is specifically 911 and not, say 211, I don’t know.
pldennison: Thanks for a response more detailed than my guess. One quibble though: Zero on a rotary phone requires ten “clicks”.
BTW: My dad showed me once how you could dial a number by rapidly pulsing the “hang up” button. It reminds me of when people in movies rap up and down on the button saying, “Hello! HELLO!”. I guess if people do that in an emergency they will eventually make ten pulses and get the operator.
These are known as N11 Service codes. They are used to provide three digit special access services. In the US, the FCC administers N11 codes & recognizes only 211, 311, 511 & 711 as nationally assigned. Other codes with traditional uses:
211: Community information & referral service
311: Non-emergency police & other governmental services
411: Local directory assistance
511: Traffic & transportation information
611: Repair service
711: Telecommunications Relay Service
811: Business office & auto number feedback
911: Emergency
= = = =
811 is one of my favorites. This is the number you can dial at almost any phone and have an automated voice tell you what number you are calling from.
Don’t omit 011, used to signify overseas calls.
Oh, and the number is called “Nine one one” rather than “Nine eleven” so that small children being asked to dial it by a grownup won’t look for a button marked 11.
And so people don’t think it’s the phone number of your Porche dealer 
711: Telecommunications Relay Service
I was waiting for this. I wonder if its connected yet?
Hm. I found some good info on the history of 911
Basically, it had to be an N11 as Attryant said. People felt that 9 would be easiest to “clear for access” for the phone companies at the time. 9 is also relatively easy to find in the dark when you’re on a rotary. Just find the last hole and move back one. Obviously 0 and 1 would be even easier to find, but from what I can tell, the phone companies already had functions assigned to those digits being dialed first.
The British system was to dial 9-9-9 (At least, it was in the early 60s, when Dial 9-9-9 was on American TV). The phone company did consider this, but decided that someone in a panic might forget how many 9’s were dialed. That was one reason they gave for choosing 9-1-1.
Sure, but then you could just keep dialing 9 until someone picks up right? Just like when you want to get a taxi when you’re drunk in Reno; keep dialing 7 until you hear someone talking.
The history of the United States’ first 911 call along with a mention of how the British were way ahead of the U.S. in this area (by 31 years) can be found at
http://www.911dispatch.com/911_file/haleyville.html
I realize this is not relevant to rotary phones, but on a touch-tone phone, 911 is harder to dial by mistake, since 9 and 1 are on opposite sides of the touch-pad.
I have now a similar feature on my cell phone, where I have to press two keys that are distant from each other in order to “unlock” the phone.
By the way, any explanation as to why the phone touchpad is not the same order as a calculator? (I think perhaps Cecil has discussed this…)
Nevermind children; you are also told to say 9-1-1 when learning CPR so that you don’t scream at somebody to go dial 9-eleven, causing that person to waste valuable seconds searching for an “eleven” key.
If I was administering CPR, the instructor told me I had to say "Quick! Go dial nine-one-one and stay on the line!. If I said nine-eleven, I would fail the CPR class.
I bet this has something to do with Jan Lucasiewicz and his goofy Reverse Polish Notation invention. If you’ve ever noticed, accountant style adding machines act like they have a mind of their own unless you know that the operators need to entered after the digits.
A very common GQ question.
Calculator keypads vs. phone buttons—WHY?
Keyboards and Keypads
123 or is it 789
Numeric key pads on phones/computers…
numeric keypads
If Zero comes before One, why is it after 9?
I recall a housemate (:wally)of mine coming home drunk, meaning to dial 011-phone sex and dialing 911 by mistake. The cops sure didn’t care for that brand-new hand made bhong on the living room table. 
Damn, I screwed that quote up good! Some of the “quote” is my response!
A lot of people can’t find 11 on their dial.
911 was invented by Porsche
Oh alright if you must know the answer from the web:
http://www.911dispatch.com/911_file/911history.html#anchor229284
"Why the dialing code 9-1-1? This is a real hard question to answer and my first response is: Why not?
Everyone has his or her own access code and I have heard most of them. But the truth is that AT&T and USITA had to come
up with one for the telephone system–for the total system.
I was an engineer for AECO Gen Tel Labs when I became part of this task force. And believe me, this was no snap; it took
much time to resolve. No one wanted to give in, but as time went on, we all came to the same understanding. The access code
had to be three digits. The first digit had to be an N digit, meaning it had to be one of the digits 2 through 9. The digit 1 or 0
could not be used. The second and third digits had to be 1.
So the real problem was what was the first digit going to be and the task force set out to resolve this problem.
It came down to the fact that the digit 9 was the easiest to clear for access, because in many systems it was already clear; in
others, equipment changes were small. With this, 9-1-1 was selected and work started to make this an access code back as far
as the late '50s.
There was one other factor that helped resolve this, and it was the location of this digit on the dial or keypad.
If one had to dial 9-1-1 in the dark, all one had to do was place the finger in the dial, slide the finger from the one position all
the way around to the zero position, back up one step and this would be the ninth position or digit 9.
Then the call originator would again place the finger into the lst position; this would he the digit one–and dial it two times. The
outcome would he 9-1-1.
With the keypad, the call originator would locate the lower righthand key position (the # or pound key) and move straight up to
the next position, which is the digit 9. Then move the finger so the upper-most left hand side, which is the digit one. With this
method, one could easily dial 9-1-1 in the dark."