| Table ID No. | MCAG | Legal Name | Entity Name | Government Description |
| 1438 | 1549 | Icicle Irrigation District | Icicle Irrigation District | Irrigation and Reclamation District |
| 1653 | 1734 | Port of Illahee | Illahee, Port of | Port District (Includes Airports) |
| 326 | 0547 | City of Ilwaco | Ilwaco, City of | City/Town |
| 1654 | 1748 | Port of Ilwaco | Ilwaco, Port of | Port District (Includes Airports) |
| 1896 | 1864 | Inchelium School District No. 70 | Inchelium School District No 70 | School Districts |
| 2219 | 2201 | Inchelium Water District | Inchelium Water District | Water/Sewer District |
| 50 | S250 | Indeterminate Sentence Review Board | Indeterminate Sentence Review Board | Agency, Commission, or Board |
| 1897 | 2032 | Index School District No. 63 | Index School District No 63 | School Districts |
| 327 | 0675 | Town of Index | Index, Town of | City/Town |
| 51 | S086 | Governor's Office of Indian Affairs | Indian Affairs, Governors Office of | Agency, Commission, or Board |
| 1655 | 1735 | Port of Indianola | Indianola, Port of | Port District (Includes Airports) |
| 52 | S190 | Board of Industrial Insurance Appeals | Industrial Insurance Appeals, Board of | Agency, Commission, or Board |
| 53 | S155 | Department of Information Services | Information Services, Department of | Agency, Commission, or Board |
| 54 | S160 | Office of the Insurance Commissioner | Insurance Commissioner, Office of the | Agency, Commission, or Board |
| 2102 | 0269 | Intercity Transit | Intercity Transit | Transit/Transportation Authority |
| 328 | 0558 | Town of Ione | Ione, Town of | City/Town |
| 2220 | 2318 | Irvin Water District No. 6 | Irvin Water District No 6 | Water/Sewer District |
| 1439 | 1550 | Isenhart Irrigation District | Isenhart Irrigation District | Irrigation and Reclamation District |
| 630 | 0123 | Island County | Island County | County |
| 149 | 0032 | Island County Cemetery District No. 1 | Island County Cemetery District No 1 | Cemetery District |
| 150 | 0033 | Island County Cemetery District No. 2 | Island County Cemetery District No 2 | Cemetery District |
| 679 | 0905 | Island County Diking District No. 1 | Island County Diking District No 1 | Diking/Drainage District |
| 680 | 0906 | Island County Diking District No. 2 | Island County Diking District No 2 | Diking/Drainage District |
| 681 | 0907 | Island County Diking District No. 3 | Island County Diking District No 3 | Diking/Drainage District |
| 682 | 0908 | Island County Diking District No. 4 | Island County Diking District No 4 | Diking/Drainage District |
| 683 | 0909 | Island County Drainage District No. 1 | Island County Drainage District No 1 | Diking/Drainage District |
| 684 | 0913 | Island County Drainage District No. 5 | Island County Drainage District No 5 | Diking/Drainage District |
| 685 | 0914 | Island County Drainage District No. 6 | Island County Drainage District No 6 | Diking/Drainage District |
| 842 | 0951 | Island County Emergency Services Communications Center | Island County Emergency Services Communications Center | Emergency Management Services |
| 954 | 1113 | Island County Fire Protection District No. 1 | Island County Fire Protection District No 1 | Fire Protection District |
| 955 | 1114 | Island County Fire Protection District No. 2 | Island County Fire Protection District No 2 | Fire Protection District |
| 956 | 1115 | Island County Fire Protection District No. 3 | Island County Fire Protection District No 3 | Fire Protection District |
| 957 | 1117 | Island County Fire Protection District No. 5 | Island County Fire Protection District No 5 | Fire Protection District |
| 1351 | 1507 | Housing Authority of Island County | Island County Housing Authority | Housing Authority |
| 2137 | 2805 | Island County Water Conservation Board | Island County Water Conservation Board | Water Conservation Board |
| 1785 | 2476 | Island Regional Planning Council | Island Regional Planning Council | Regional Planning Council |
| 2103 | 0499 | Island Transit | Island Transit | Transit/Transportation Authority |
| 1511 | 1273 | Issaquah Library Capital Facilities Area | Issaquah Library Capital Facilities Area | Library District |
| 1898 | 1919 | Issaquah School District No. 411 | Issaquah School District No 411 | School Districts |
| 329 | 0399 | City of Issaquah | Issaquah, City of | City/Town |