Who invented the "@" sign found on keyboards?  How did it come to mean
"at"? How long
has it been around? What is the history of this character?

Dear Marv, 

The symbol @ (official term: asperand) - as you know it, as part of
email addresses - was introduced by Ray Tomlinson of Bolt Beranek and
Newman in 1971, as a separator symbol for one of the first e-mail
systems (SOURCE : Ray Tomlinson's Homepage, "Frequently Made
Mistakes", <http://openmap.bbn.com/~tomlinso/ray/mistakes.html>).

However, the symbol existed before, and with the meaning of "at" in
Anglo-Saxon and Northern European cultures: "A commonly accepted
theory is that the symbol is derived from the Latin preposition "ad"
(which means "to" rather than "at"). The @ is supposed to be a
ligature developed by transcribing monks. However no document showing
this usage has been presented.

A more recent idea concerning the history of the @ symbol has been
proposed by Giorgio Stabile, a professor of history in Rome. He claims
to have traced the symbol back to the Italian Renaissance in a
Venetian mercantile document signed by Francesco Lapi on May 4, 1536.
The document talks about commerces with Pizarro and in particular the
price of an @ of wine in Peru. The symbol is still called arroba in
Spanish and Portuguese, and it represents a unit of weight with the
same name (1 arroba = 25 U. S. pounds), an old (Antonio Nebrjia,
Salamanca, 1492) Spanish/Latin dictionary translates arroba with
amphora. Under this view, the symbol was used to represent one
amphora, which was a unit of weight or volume based upon the capacity
of the standard terracotta jar. The symbol came into use with the
modern meaning "at the price of" in northern Europe."
(SOURCE: Wikipedia, @, <http://en.wikipedia.org/wiki/@>). 

You can read more about the history of @, @: 
"WHERE IT&#8217;S AT Names for a common symbol" , World Wide Words,
<http://www.worldwidewords.org/articles/whereat.htm>

Ray Tomlinson's Homepage
<http://openmap.bbn.com/~tomlinso/ray/home.html> 

The Guardian: Does the symbol @ have a name? If not, any suggestions?
<http://www.guardian.co.uk/notesandqueries/query/0,5753,-1773,00.html> 

I hope this answers your question. Please contact me if you need any
further clarifications on this answer before you rate it. Search
terms: "the at sign", asperand

Why was i banned from giving an answer to this question Who has the
power to lock other users from posting an answer.

Here is some information i found on the internet First they detail why
it was chosen for then internet then look further back for itls
history.

http://www.webopedia.com/DidYouKnow/Internet/2002/HistoryofAtSign.asp
In 1972, Ray Tomlinson sent the first electronic message, now known as
e-mail, using the @ symbol to indicate the location or institution of
the e-mail recipient. Tomlinson, using a Model 33 Teletype device,
understood that he needed to use a symbol that would not appear in
anyone's name so that there was no confusion. The logical choice for
Tomlinson was the "at sign," both because it was unlikely to appear in
anyone's name and also because it represented the word "at," as in a
particular user is sitting @ this specific computer.
However, before the symbol became a standard key on typewriter
keyboards in the 1880s and a standard on QWERTY keyboards in the
1940s, the @ sign had a long if somewhat sketchy history of use
throughout the world. Linguists are divided as to when the symbol
first appeared. Some argue that the symbol dates back to the 6th or
7th centuries when Latin scribes adapted the symbol from the Latin
word ad, meaning at, to or toward. The scribes, in an attempt to
simplify the amount of pen strokes they were using, created the
ligature (combination of two or more letters) by exaggerating the
upstroke of the letter "d" and curving it to the left over the "a."

Other linguists will argue that the @ sign is a more recent
development, appearing sometime in the 18th century as a symbol used
in commerce to indicate price per unit, as in 2 chickens @ 10 pence.
While these theories are largely speculative, in 2000 Giorgio Stabile,
a professor of the history of science at La Sapienza University in
Italy, discovered some original 14th-century documents clearly marked
with the @ sign to indicate a measure of quantity - the amphora,
meaning jar. The amphora was a standard-sized terra cotta vessel used
to carry wine and grain among merchants, and, according to Stabile,
the use of the @ symbol ( the upper-case "A" embellished in the
typical Florentine script) in trade led to its contemporary meaning of
"at the price of."

While in the English language, @ is referred to as the "at sign,"
other countries have different names for the symbol that is now so
commonly used in e-mail transmissions throughout the world. Many of
these countries associate the symbol with either food or animal names.


Afrikaans - In South Africa, it is called aapstert, meaning "monkey's tail" 
Arabic - The @ symbol does not appear on Arabic keyboards, only
keyboards in both Arabic and English. The Arabic word for @ is fi, the
Arabic translation of at
Bosnian, Croatian and Serbian - In these countries, it is referred to
as the "Crazy I"
Cantonese - In Hong Kong it is generally referred to as "the at sign,"
just as in England and America
Catalan - In Catalonia, it is called arrova, a unit of weight 
Czech - In the Czech Republic, it is called zavinac, meaning
"rollmop," or "pickled herring"
Danish - It is called alfa-tegn, meaning "alpha-sign" or snabel-a,
meaning "elephant's trunk" or grisehale, meaning "pig's tail"
Dutch - Since English is prominent in the Netherlands, the English
"at" is commonly used. However, the Dutch also call it apestaart,
meaning monkey's tail," apestaartje, meaning "little monkey's tail" or
slingeraap, meaning "swinging monkey"
French - In France, it is called arobase the name of the symbol. It is
also referred to as un a commercial, meaning "business a", a enroule,
meaning "coiled a", and sometimes escargot, meaning "snail" or petit
escargot, meaning "little snail"
German - In Germany, it is called Affenschwanz, meaning "monkey's
tail" or Klammeraffe, meaning "hanging monkey"
Greek - In Greece, it is called papaki, meaning "little duck" 
Hebrew - It is shablul or shablool, meaning "snail" or a shtrudl,
meaning "strudel"
Hungarian - In Hungary, it is called a kukac, meaning "worm" or "maggot" 
Italian - In Italy it is called chiocciola, meaning "snail" and a
commerciale, meaning "business a"
Japanese - In Japan, it is called atto maaku, meaning "at mark" 
Mandarin Chinese - In Taiwan it is called xiao lao-shu, meaning
"little mouse," lao shu-hao, meaning "mouse sign," at-hao, meaning "at
sign" or lao shu-hao, meaning "mouse sign"
Norwegian - In Norway, it is called either grisehale, meaning "pig's
tail" or kro/llalfa, meaning "curly alpha." In academia, the English
term "at" is widely used
Polish - In Poland, it is called malpa, meaning "monkey." It is also
called kotek, meaning "little cat" and ucho s'wini, meaning "pig's
ear"
Portuguese - In Portugal it is called arroba, a unit of weight 
Romanian - In Romania, it is called la, a direct translation of English "at" 
Russian - Russians officially call it a kommercheskoe, meaning
"commercial a", but it is usually called sobachka, meaning "little
dog"
Spanish -- Like in Portugal, in Spain it is called arroba, a unit of weight 
Swedish - The official term in Sweden is snabel-a, meaning "trunk-a,"
or "a with an elephant's trunk"
Thai - There is no official word for it in Thai, but it is often
called ai tua yiukyiu, meaning "the wiggling worm-like character"
Turkish - In Turkey, most e-mailers call it kulak, meaning "ear"

The web page also gives other links for further explantations 

For more information, also see:
A Brief History of @ 
@ -- A Sign of the Times 
From Whence Comes The At Sign @ ? 
Who Put the @ in Your E-Mail? 
Where It's At: Names for a Common Symbol 

I typed in the 3 words, "at symbol" history, to get his information.

http://art-bin.com/art/asignoftimes.html also says the sign might go
back to latin roman times.

Hi Elaphotomus,
That was fantastic, thank you, from me, just another commenter.
Only Google Answers Researchers, whose user names appear in blue and
are underlined, may post "answers".  We commenters with black user
names, can just post comments.  It is a two class society (check out
the FAQs).

But again, my compliments for your effort, the most comprehensive
compilation on the subject I have seen.  :)
Myoarin

elaphotomus-ga 
Further to myoarin's comments , the Google Answer service has been in existance
since 2002. After an initial pilot/beta test, Google recruited 500
official researchers to formally answer the questions on this site.

Commenters like myoarin, yourself and myself can add comments which
may add (or in some cases detract) from the original answer. They can
also give the questioner very useful information if no Official
Researcher wishes to answer
a particular question.

In many cases (and yours is one example) a commenter will provide an
information which in effect answers a question. In this case the
questioner gets his/her answer for free if the question does not get
an "official answer". In most cases if a commenter gives a relevant
answer, official researchers will refrain from posting an "official
answer". A questioner has also the option to "expire" a question which
simply means no further updates can be made to the question (although
the information still resides on the system)

Google has up to now choose not to replenish the original 500
researchers which it recruited in 2002. Quite a few questions come to
Google Answers
from people wishing to be Google Answer Researchers and the answer has
always been "Thank You but no Thank you"

In my humble opinion it is high time Google hired more researchers. This is 
certainly not meant as a criticism of the current Google Researchers
but just to point out the large number of questions which go
unanswered and also the fact that core group of remaining researchers
probably number less than 30.

I fully accept the fact that my comment will have absolutely no influence on
the Google Corporation who can like most other trans national
corporations do whatever they want.

Regards

Mongolia

Marv,
There is a typo in the first line of the answer.  The @ is called "ampersand".

Mongolia, I think that there actually have been some new Researchers. 
Hagan-ga appeared a while ago with a first and several subsequent and
very savvy legal answers.
Myoarin

Correcting myoarin-ga's correction: the "@" sign is indeed called an "asperand."

"Ampersand" is the name of the "&" sign (meaning "and") not the "@"
sign (meaning "at")

OH, geez, you're right, atk-ga!  Thanks, and my apologies, also to Politicalguru.
Maybe I should have chosen the user name "half-cocked" instead of
Myoarin