Complex sentence: Before 1925, Weott had been known informally as Helm's Mill or Helm's Camp, then as McKee's Mill (named for Ernest McKee, who operated a shingle mill just east of lower Weott, the building of which still stands).
Split into simpler sentences: Before 1925, Weott had been known informally as Helm's Mill or Helm's Camp. Then as McKee's Mill (named for Ernest McKee, who operated a shingle mill just east of lower Weott, the building of which still stands).