So check this page out.

https://egov.uscis.gov/cris/processTimesDisplayInit.do

Scroll all the way down to the bottom and enter the facility that your application was sent to.
I looked up the processing times for Nebraska, and here is what i found for the i-821d
It shows the last application processed and from which month. the last application processed shows from September 4, 2014. Now im aware that this is outdated but im not sure how outdated. It shows that the page was updated as of Feb 11, 2015. But it additionally says that this info is from December 31, 2014. Im not sure which date is more correct.