Iowa allows 5% as max interest. Maine is beautiful territory though.
A bit more complicated than that?
Iowa Code 535.2
" Except as provided in subsection 2, the rate of interest shall be five cents on the hundred
by the year in the following cases, unless the parties shall agree in writing for the payment
of interest at a rate not exceeding the rate permitted by subsection 3:"
"3. a. (1) The maximum lawful rate of interest which may be provided for in any written
agreement for the payment of interest entered into during any calendar month commencing
on or after April 13, 1979, shall be two percentage points above the monthly average ten-year
constant maturity interest rate of United States government notes and bonds as published by
the board of governors of the federal reserve system for the calendar month second preceding
the month during which the maximum rate based thereon will be effective, rounded to the
nearest one-fourth of one percent per year."
In Oregon it is "nine percent per annum" unless "otherwise agreed."