what is the legal amount of cash that a person is allowed to carry and
transport from state to state or city to city?

unlimited

There is no legal limit of cash that a person can carry or transport
from city to city and state to state.

However, if you are travelling internationally, and are carrying
$10,000 or more in cash/bonds/etc., you must inform Customs.  It is
not illegal to carry the cash; you just have to inform Customs (which
informs the IRS) that you are carrying that much.

Check out this site for more info:

http://www.customs.gov/linkhandler/cgov/toolbox/publications/travel/currency_reporting.ctt/currency_reporting.doc

When crossing the border, I'd always worried about what constituted
$10,000 worth of monetary instruments.  After all, if you counted
credit cards one might easily have a single one with a line-of-credit
larger than $10,000 and it would be even easier to accumulate that
amount with 2 or 3 credit cards.

But according to "Section 1956. Laundering of monetary instruments,"
of the U.S. Code dated Jan. 22, 2002:
"the term ''monetary instruments'' means (i) coin or  currency of the
United States or of any other country, travelers' checks, personal
checks, bank checks, and money orders, or (ii) investment securities
or negotiable instruments, in bearer form or otherwise in such form
that title thereto passes upon delivery;"

FindLaw
U.S. Federal Code
http://caselaw.lp.findlaw.com/scripts/ts_search.pl?title=18&sec=1956

So, don't take along that year-end bonus check but it appears that
you're safe with the credit cards!

Best regards,

Omnivorous-GA