| Year | Won | Margin | Democratic | Republican | Total |
|---|---|---|---|---|---|
| 2024 | R | 291 | 805 | 1,134 | |
| 2020 | R | 324 | 834 | 1,178 | |
| 2016 | R | 239 | 671 | 1,019 | |
| 2012 | R | 371 | 639 | 1,061 | |
| 2008 | R | 430 | 648 | 1,110 | |
| 2004 | R | 370 | 755 | 1,138 | |
| 2000 | R | 359 | 679 | 1,090 | |
| 1996 | D | 485 | 398 | 1,040 | |
| 1992 | R | 374 | 377 | 1,038 | |
| 1988 | R | 417 | 470 | 897 | |
| 1984 | R | 369 | 700 | 1,073 | |
| 1980 | R | 394 | 622 | 1,140 | |
| 1976 | R | 508 | 612 | 1,166 | |
| 1972 | R | 355 | 665 | 1,069 | |
| 1968 | R | 436 | 619 | 1,120 | |
| 1964 | D | 775 | 442 | 1,220 | |
| 1960 | R | 606 | 712 | 1,318 | |
| 1956 | R | 538 | 793 | 1,331 | |
| 1952 | R | 415 | 911 | 1,329 | |
| 1948 | R | 544 | 623 | 1,184 | |
| 1944 | D | 567 | 492 | 1,060 | |
| 1940 | D | 785 | 518 | 1,307 | |
| 1936 | D | 983 | 362 | 1,411 | |
| 1932 | D | 854 | 470 | 1,343 | |
| 1928 | R | 515 | 880 | 1,408 | |
| 1924 | R | 521 | 738 | 1,470 | |
| 1920 | R | 498 | 821 | 1,355 | |
| 1916 | D | 870 | 557 | 1,470 | |
| 1912 | R | 310 | 348 | 859 | |
| 1908 | R | 242 | 470 | 759 | |
| 1904 | R | 195 | 568 | 842 | |
| 1900 | R | 343 | 419 | 791 | |
| 1896 | R | 470 | 551 | 1,027 | |
| 1892 | R | 253 | 402 | 847 | |
| 1888 | — | — | — | — | |
| 1884 | — | — | — | — | |
| 1880 | — | — | — | — | |
| 1876 | — | — | — | — |
Gilliam County sits in the high desert east of the Cascades, where fewer than 2,000 residents have delivered Republican presidential margins above 40 points in recent cycles, reflecting a pattern common across Oregon's sparsely settled wheat-belt interior.
The Democratic margin in Gilliam County peaked at forty-four points in 1936. By 2000 the county had flipped, voting Republican for the first time in many years. The 2024 margin was forty-five points, the most Republican-leaning result in the county's modern history.
The economic context is the key. Gilliam County's median household income of $66,917 sits well below state and national norms, and 15% of residents live below the federal poverty line. The shift here is part of a broader realignment of working-class places across the country. The county's voting pattern over the last decade is most similar to that of Wright County and Morrow County.