Jaco was born in Cornwall, in 1729.
In 1746, he began to hear Methodist preaching, from the traveling preachers who roamed all over England. He had not come to faith, but he was close. He wanted to know more, had respect for the preachers, but was not willing to surrender all. In his papers, he reminds Wesley of an incident in Cornwall. Here is John Welsey's account:
"I rode to Newlyn [Jaco's hometown], a little town on the south sea, about a mile from Penzance. At five I walked to a rising ground, near the seashore, where was a smooth white sand to stand on. An immense multitude of people was gathered together; but their voice was as the roaring of the sea. I began to speak, and the noise died away: But before I had ended my prayer, some poor wretches of Penzance began cursing and swearing, and thrusting the people off the bank. In two minutes I was thrown into the midst of them; when one of Newlyn, a bitter opposer till then, turned about and swore, “None shall meddle with the man: I will lose my life first.” Many others were of his mind: So I walked an hundred yards forward, and finished my sermon without any interruption."
Peter Jaco was one of the young men who threatened the mob if they did not let Wesley preach.
One day on his way to church, Jaco seemed to hear the Lord say, "Jesus Christ died for the vilest sinner." And Jaco replied, "Then I am the wretch for whom He died!"
Jaco was called to preach, but doubted his ability. He thought he would be an occasional helper, but John and Charles Wesley wanted to see him as a full-time traveling preacher.
Here is Jaco's account of his ministry:
"I had many difficulties to struggle with. In some places the work was to begin, and in most places being in its infancy, we had hardly the necessities of life; so that after preaching three or four times a day and riding thirty or forty miles, I have often been thankful a little clean straw with a canvas sheet to lie on. Very frequently we also had violent opposition. At Warrington I was struck so violently with a brick on the breast that the blood gushed out through my mouth, nose, and ears. At Grampound, I was pressed for a soldier [essentially kidnapped and forced into the army--normally reserved for vagrants and petty criminals]...though I was honorably acquitted... it cost me a pretty large sum of money as well as much trouble
"For many years I was exposed to various other difficulties and dangers. But having obtained help from God, I continue to this day in His service. At present, I find my mind as much devoted to Him as I ever did. I see and feel the necessity of a greater conformity to Christ. May I never be satisfied till I awake up after His likeness!"
Jaco died in 1781.