The line graph portrays the growing number of population, which is measured in thousands over 60-year period in Columbia, Yamhill, and Washington. Overall, the main fact that stands out is that in all counties experienced an increase in the sum of inhabitants. Moreover, Washington's population rose significantly among two other counties.
To begin with, in 1940, the number of residents in Washington stood at 75,000. Then, it increased gradually to roughly 122,000 by the end of 1970. Subsequently, the population of Washington showed a dramatic growth, which hit a high of around 245,000 people in the end of the period.
Turning to Yamhil and Columbia, both of which experienced a similar pattern from time to time. Firstly, they stood at 30,000 and 25,000 respectively in 1940. Over the following 30 years, Yamhil and Columbia grew slightly to 45,000 and 35,000 and then rose dramatically to 90,000 and 77,000 successively in the timeframe shown.