I think it was in late 1940s? People had flocked to work in Washington because of the war, and there wasn't enough housing in the city proper. Also people wanted more room to raise their baby boom kids! But pockets stayed rural even after the housing tracts came in. The mascot of Walter Johnson High School on Democracy Blvd is actually a cow, because dairy cows used to roam the adjacent fields when it was built in 1956.