TRAC is a data-gathering, data research and data distribution organization at Syracuse University. Its Immigration Project is a multi-year effort to obtain very detailed information from the government, check it for accuracy and completeness, and then make it available in an understandable way.
TRAC lists the number of ICE detainers that each county in the country has complied with, organized by detention center: http://trac.syr.edu/phptools/immigration/detain/
Select the state you are researching in the left-most column, then the “County-Facility Detainer Sent” in the middle column. Note that there may be more than one facility in a given county, so add those up if you are looking to determine the total number of detainers complied with by a particular county. Then you can select “Detainer Refused” in the right-most column. The last column will allow you to calculate the minimum amount of ICE detainers the county complied with. Note that the number is likely higher, as there is always a significant amount of detainers listed as “Not Known” with regard to whether they were complied with.
The Immigrant Legal Resource Center also has a useful National Map of Local Entanglement with ICE that allows the public to locate detailed information on a county-by-county basis.