23 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Centralia | 1 | 19,227 | 18,322 | 0.87% | 2,523 | 8 | City |
| Centralia | 2 | 19,227 | 18,397 | 0.87% | 2,523 | 8 | City |
| Chehalis | 3 | 7,776 | 7,428 | 0.76% | 1,339 | 6 | City |
| Chehalis | 4 | 7,776 | 7,479 | 0.76% | 1,339 | 6 | City |
| Grand Mound | 5 | 3,557 | 3,957 | 1.08% | 857 | 4 | CDP |
| Fords Prairie | 6 | 3,063 | 2,582 | 2.48% | 822 | 4 | CDP |
| Winlock | 7 | 2,685 | 1,818 | 6.76% | 2,078 | 1 | City |
| Winlock | 8 | 2,685 | 1,834 | 6.76% | 2,078 | 1 | City |
| Napavine | 9 | 2,217 | 1,894 | 2.88% | 767 | 3 | City |
| Napavine | 10 | 2,217 | 1,905 | 2.88% | 767 | 3 | City |
| Morton | 11 | 1,101 | 1,035 | 1.1% | 1,341 | 1 | City |
| Morton | 12 | 1,101 | 1,040 | 1.1% | 1,341 | 1 | City |
| Mossyrock | 13 | 810 | 769 | 0.87% | 1,177 | 1 | City |
| Mossyrock | 14 | 810 | 773 | 0.87% | 1,177 | 1 | City |
| Toledo | 15 | 799 | 632 | 4.17% | 2,028 | 0 | City |
| Toledo | 16 | 799 | 636 | 4.17% | 2,028 | 0 | City |
| Vader | 17 | 707 | 618 | 2.46% | 761 | 1 | City |
| Vader | 18 | 707 | 620 | 2.46% | 761 | 1 | City |
| Pe Ell | 19 | 676 | 644 | 0.75% | 1,144 | 1 | Town |
| Pe Ell | 20 | 676 | 648 | 0.75% | 1,144 | 1 | Town |
| Onalaska | 21 | 593 | 431 | -0.34% | 370 | 2 | CDP |
| Packwood | 22 | 60 | 294 | -23.08% | 60 | 1 | CDP |
| Mineral | 23 | 36 | 135 | -23.4% | 54 | 1 | CDP |
Centralia is the largest city in Lewis County, with a population of 19,227.
Mineral is the smallest city in Lewis County, with a population of 36.
There are 23 cities in Lewis County, Washington.