I work in a law firm and have become intrigued with "legal size"
paper.  My question pertains to the history, meaning and significance
of what we call legal sized paper.  First, when was legal sized paper
first used?  What is the "history" of legal-sized paper? Second, and
related, why is it 8.4x14 as opposed to the standard letter size of
8.5x11?  Third, why are legal pads traditionally yellow as opposed to
white?

The answer(s) I am looking for would include relevant dates, places
and people.  The standard for your answer should be, would a lawyer
(or interested non-lawyer) find the answer interesting, funny, etc. 
Details are the key.  Thanks.

Dear yoyo thank you for this interesting question which I have
wondered about in the past too! Here are the answers:

1.As for the date when legal sized paper was first used:
 “We note that by the 1870s a paper size called legal cap or legal
blank had emerged that was 8-1/2 inches wide and anywhere from 13 to
16 inches long.”

2. 8.4x14 Vs 8.5x11
 “The situation with legal size (8-1/2x14) is equally murky. It
arguably does   derive from foolscap, a traditional paper size" also
"I believe our standard 8-1/2x11 typing paper is a quarter sheet of
what eighteenth and nineteenth-century papermakers would call `writing
medium.' Printers used a medium sheet of 18x23 inches but stationers
preferred a smaller version of medium measuring 17x22 inches.... "

3.Why do lawyers use yellow pads? 
"Because they are allegedly (like the use of that lawyerly term?)
easier on the eyes than white paper. And for people who have to write
and read a lot, it makes sense to use something that's easier on the
eyes."
http://www.straightdope.com/mailbag/mattorney.html


Some of the humour I stumbled across too:
"lawyers use legal size because they need 14 inches to say what
ordinary folks can fit in 11."

“If 8.5 x 14 paper is considered 'legal' size is everything else
illegal? Will we go to jail if we use illegal paper? Will the paper
police pick us up or will we just be shredded?”
http://www.gadzillionthings.net/Think153.html

I hope this answers your question which I enjoyed researching too !

THX1138

Search Term used:
"lawyers write on yellow"  (Believe it or not!)
://www.google.com/search?hl=en&lr=&as_qdr=all&q=%22lawyers+write+on+yellow%22+&btnG=Google+Search

The United States and Canada are today the only industrialized nations
in which the ISO standard paper sizes are not yet widely used. In U.S.
office applications, the paper formats "Letter" (216 × 279 mm),
"Legal" (216 × 356 mm), "Executive" (190 × 254 mm), and
"Ledger/Tabloid" (279 × 432 mm) are widely used today.

The historic origins of the 216 × 279 mm U.S. Letter format [ and
presumably Legal ], and in particular its rationale, seem rather
obscure.
http://www.cl.cam.ac.uk/~mgk25/iso-paper.html

In some jurisdictions these days it is "illegal" (actually against the
court rules or filing rules) to file legal papers on legal paper. You
have to use 8 1/2 x 11.

weisstho-ga

While not a complete answer, consider the following:  I work in the
legal field.  Originally, contracts were almost always written out on
14" paper.  (No, I don't know why.)  Legal came to differentiate
standard documents from contracts.  Now, having said that, I hate
legal pads...it's almost impossible to utilize one on one's lap.  A
desk is a must.

Helena