From the explanation found about Brooklyn at http://www.iltrails.org/McHenry/crystlk.htmhttp://www.iltrails.org/McHenry/crystlk.htm it was the North Part of today's Crystal Lake which was first called Dearborn, then Nunda (incorporated 1874) then, North Crystal Lake after 1901.
Crystal Lake was incorporated 1874, on the 1850 Census it was called Brooklyn.
Names of the Township:Late 1830's Nunda township was first named Brooklyn, changed to Nunda 1840.Nunda was the principal settlement of the township from 1855-1908 when it became known as North Crystal Lake.For a more thorough answer to your question, please go to the URL given above.
I know that two of the sons of Thomas BARNES & Julia MOORE enlisted in the Civil War and were called "of Nunda".Any help with Thomas BARNES & Julia MOORE (and family) after their listing in the 1850 census is greatly appreciated.
The new "Illinois Trails" website is very good, especially since there is no website for McHenry County at rootsweb.