U.S. persons are required to report their worldwide income on their U.S. (and state) income tax returns. All income is taxable unless the Internal Revenue Code specifically excludes them.
Selling rental properties overseas is not any different from selling domestic rental properties, you report the sale on Part III of Form 4797, see https://www.irs.gov/pub/irs-pdf/i4797.pdf. The fact that it was your primary residence until 2009 is not relevant as you did not live in it at anytime within the last 5 years. IRS assumes depreciation has been deducted on the property whether or not you actually took depreciation on your previous years tax returns, their phrase is "allowed or allowable". But you may take a catch-up depreciation this year if you didn't.
Any income tax you paid in Africa on the sale of this property may be used to offset your federal tax liabilities, but not state taxes, on Form 1116.
Unrelated to your question, if you have an overseas bank account with balance exceeding $10,000 at anytime during the year, you will have to file a Foreign Bank Account Report (FBAR), Form 114, with FinCEN of the U.S. Treasury. Form 114 must be filed electronically. You may also have to file a Form 8938 with your 1040 tax return.
I suggest you seek professional help to complete your tax returns this year.
