There is no inheritance tax neither on the federal level.
Federal estate tax applies only to estates with total value above $2,000,000 (for decedent died in 2008).
Inheritance is your income, but not taxable income. Please see IRS publication 525 page 33 for reference - http://www.irs.gov/pub/irs-pdf/p525.pdf
So - you do not need to claim it on your tax return and do not owe any taxes regardless or the amount.
The only situation you might owe income tax - if that amount was in tax deferred account - such as IRA or pension plan. In this case the distributed amount should be included into your taxable income and you should receive a reporting form 1099-R.
Please verify if the money were in tax deferred account.
As your mother died on Indiana - this state imposes an inheritance tax on individuals who are residents of the State of Indiana at the time of their death at different rates based on your relationship to the decedent.
However - Parents, children, stepchildren (included if decedent's date of death is after June 30, 2004), grandparents, grandchildren and other lineal ancestors and lineal descendants are eligible for an exemption of $100,000 each. - http://www.in.gov/dor/3807.htm - so there should not be inheritance tax on $90,000.
In all other situations - you will not owe any taxes.
Let me know if you need any help.
Tax Preparer
Taxes, Immigration, Labor Relations