Op-amp dominant pole bandwidth
Op amps which use dominant pole compensation have a constant gain-bandwidth product. You've cited a 5Hz dominant pole, and the LM301A datasheet gives a typical open loop voltage gain of \$160\text{V}/\text{mV} = 160,000\$. This gives a gain-bandwidth product of \$160,000 \times 5\text{ Hz} = 800,000\text{ Hz}\$. You have configured this op amp with a closed loop gain of \$|A_v| = 20\$ so the expected bandwidth is \$800,000\text{ Hz}/20 = 40,000\text{ Hz}\$, which is close to your observed -3dB point of 38kHz.