Reports in newspapers are still referring to “16 signers” of Sheriff Tom Bergin’s letter endorsing Measure 105, and ignoring the 2 Sheriffs who signed shortly after the letter was first released. For your and the public’s information, there are 18 signers of the letter, representing half of Oregon's 36 counties.
Counties whose sheriffs have signed the letter are (in alphabetical order): Clatsop, Coos, Curry, Deschutes, Douglas, Gilliam, Grant, Harney, Jefferson, Klamath, Lake, Malheur, Morrow, Sherman, Umatilla, Union, Wallowa, Wheeler.
FAIR (Federation for American Immigration Reform), in its Top Weekly News release of September 23, 2018 for email subscribers, gives a link to the Sheriff’s letter showing all 18 signatures. Here is the letter with all 18 signatures.