You can use any major US city as an example in this question.  If
property owned by the city was being offered for sale to private
owners (i.e. the city closed a park or something, zoned the land for
housing, and parceled lots out for sale), where would you go to
purchase the property?  (for instance: "county land office?")

Hi sasquatch77,

To purchase city property, you should first go to the City Hall of the
city you are interested in buying property from. Some City Halls
accommodate a Real Estate Division, which provides the information you
need for purchasing property from the city. Others will direct you to
Department where the Real Estate Division is located. For example, in
Tucson, Arizona, the  Real Estate Division is a division of the
Department of Transportation.

The following are excerpts of the procedures of various cities to buy
city property. I advise you to read the documents in their entirety
for a better understanding.

"All property that is currently not in use by a City Department and is
not needed for a future service is declared surplus and sold by the
City.

It is the responsibility of the Real Estate Division (a division of
the Transportation Department) to acquire, manage and dispose of all
City property..."
(...)
"An application and a listing of all surplus City-owned property is
available from the Real Estate Division. If you are interested in a
particular parcel, just notify us and the City will begin the sales
process."

Tucson Department of Transportation: How to buy property from the City of Tucson
http://dot.ci.tucson.az.us/realestate/SALES/SALSFYLR.HTM


In Utica, New York the City Hall provides all information for
purchasing city property:

"If you are interested in acquiring and rehabilitating properties that
are tax-delinquent and or abandoned in Utica you can do so by picking
up an application on the 1st floor of City Hall, or by e-mailing or
calling us with your mailing information and we will be glad to send
you an application or list of properties..."

City of Utica: How to purchase City Property
http://www.cityofutica.com/UrbanRenewal/Purchasing+Property.htm


"Frequently Asked Questions

Where can I get an application and list of properties?

Applications and the list of property can be picked up on the first
floor of City Hall or by calling and giving us your address and we
will mail them to you. Click here to download the application."
(...)
"What do I need to submit an application?

You need the completed application, developer's fee and proof of
financing to show hat you have the funds to cover your bid and
improvements.  Applications will not be accepted without all of the
above."

City of Utica: Urban Renewal - Frequently Asked Questions
http://www.cityofutica.com/UrbanRenewal/FAQ.htm


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I hope the information provided is helpful. If you have any questions
regarding my answer please don?t hesitate to ask before rating it.

Best regards,
Rainbow-ga

thanks a bunch