Hoffman Estates is a previously abandoned Chicago area Sears furniture warehouse.  The Obama Foundation leased, then re-upped the lease, to use the facility to store all the paper documents from the Obama administration {Location Link}.

The Obama administration told the National Archives and Records Administration (NARA) they were going to upload the documents into a digital form for use in the Obama library.  The paper documents were, still are, held at the Hoffman Estates warehouse while this digitization process took place.  It should be noted, the Obama Foundation has never digitized the records, hence they renewed the warehouse lease.

Contrast against the DOJ-NSD legal position about classified records held in the secure facility of Mar-a-Lago, a 2018 letter {Obama.org pdf here} from the Obama Foundation to the NARA is an example of the two-tiered selective justice system.  Within the 2018 letter the Obama team admit to storing both “classified and unclassified” documents at the warehouse: [Page #2, bullet-point 7]