1 9 5 5 ▁Clark ▁D . ▁Con nelle e ▁▁ 1 9 5 5 – 1 9 5 6 ▁J . ▁Wil mer ▁C ron in ▁▁ 1 9 5 6 – 1 9 5 8 ▁R . ▁Lee ▁Mitchell ▁▁ 1 9 5 8 – 1 9 5 9 ▁Robert ▁P . ▁At kins ▁▁ 1 9 5 9 – 1 9 6 4 ▁George ▁B . ▁Adams , ▁Jr . ▁▁ 1 9 6 4 – 1 9 6 5 ▁Robert ▁H . ▁Krie ger ▁▁ 1 9 6 5 – 1 9 6 7 ▁William ▁Cooper , ▁Jr . ▁▁ 1 9 6 7 – 1 9 6 8 ▁Warren ▁Par r ish ▁▁ 1 9 6 8 – 1 9 6 9 ▁John ▁A . ▁Fer oll ▁▁ 1 9 6 9 – 1 9 7 0 ▁William ▁Cooper , ▁Jr . ▁▁ 1 9 7 0 – 1 9 7 1 ▁Warren ▁Par r ish ▁▁ 1 9 7 1 – 1 9 7 2 ▁Al phon se ▁Dem ar co ▁▁ 1 9 7 2 – 1 9 7 4 ▁George ▁B . ▁Adams , ▁Jr . ▁▁ 1 9 7 4 – 1 9 7 5 ▁William ▁B . ▁H ause ▁▁ 1 9 7 5 – 1 9 7 7 ▁Kent ▁F . ▁Stewart ▁▁ 1 9 7 7 – 1 9 7 8 ▁William ▁B . ▁H ause ▁▁ 1 9 7 8 – 1 9 7 9 ▁Jerry ▁A . ▁N olan