During the May–June 2016 International Cooperative Air Quality Field Study in Korea (KORUS-AQ), pollution reached the remote Taehwa Research Forest (TRF) site. Two case studies are examined and observations clearly identify TRF and the surrounding rural areas as long-term receptor sites for severe urban pollution events. In summary, domestic emissions may be causing more pollution than by transboundary pathways, which have been historically believed to be the major source of air pollution.