After a few years, the population of the county increased sufficiently to provide him an extensive practice. As an advocate, his style of speech was described as colloquial and logical rather than rhetorical, the more common style of the day. He was always accorded the most profound attention when arguing a case, whether to a jury, a Justice of the Peace or before the judges of the highest courts. Peter Hitchcock was elected a member of the Ohio House of Representatives in 1810 and elected a member of the Ohio Senate in 1812 serving until 1815. He served as speaker of the Senate in 1815. Hitchcock was nominated for United States Senator in the legislative balloting to replace Thomas Worthington in 1814 and then the full term to replace Joseph Kerr in 1815, failing both times to attract sufficient votes. Peter Hitchcock was commissioned lieutenant colonel of the Fourth Regiment, Ohio State Militia, in 1814 and then commissioned major general, Fourth Division, Ohio State Militia, in 1816. Peter Hitchcock was elected as a Democratic-Republican from Ohio's 6th congressional district to the Fifteenth United States Congress. He was not a candidate for renomination in 1818.
Judicial service
The legislature appointed Peter Hitchcock a judge of the Supreme Court of Ohio in 1819 for a seven-year term, and reappointed him to a second term in 1826. Prior to 1831, panels of the Supreme Court traveled over the State in circuit, panels simultaneously holding sessions in different counties of the state. After 1831, it became the practice for the Supreme Court of Ohio to sit en banc at the capital. Judge Peter Hitchcock generally traveled the circuit on horseback or his own Yankee wagon. He would reach a county seat by noon or later, and immediately went to the Clerk's office. All the chancery cases and demurrers, or other papers for the Court, would be in his room and usually settled by the time Court opened the next morning. His method of preparing to hear a case was to determine the primary question in the case, review the law books, but develop his own line of reasoning. In court, he did not refuse to hear argument, but unless it was quite an important case, or he indicated a desire to hear argument, the members of the Bar were apt to submit directly to his examinations. It was rare that the court's business was not completed in a day. Partisan maneuvering kept Judge Hitchcock off the court in 1833. Instead he ran and was elected to another term in the Ohio Senate, again serving as speaker. Hitchcock was reappointed to another seven-year term on the court in 1835. In 1842, partisanship again took him off the court until 1845 when he was appointed to another seven-year term. He voluntarily retired in 1852 at the end of his fourth term. Of the twenty-eight years he served on the Supreme Court of Ohio, the last twenty-one of them were as Chief Justice. Hitchcock was a Presidential elector in 1844 for Clay/Frelinghuysen. The honorary degree of Doctor of Laws was conferred on him by Marietta College in 1845 and by Western Reserve College in 1849.
He was elected as a Whigdelegate to the Ohio constitutional convention in 1850 called to revise the 1802 constitution. In this capacity he contributed to reorganization of the judicial tribunals of the state, and still continued to discharge his duties on the bench. He was called the "Father of the constitution of 1851." One of the debates was over granting the power of the veto to the governor. As a good Whig, Judge Peter Hitchcock opposed it: The convention did not give the governor the veto in the new constitution.
Peter Hitchcock was the uncle of Seabury Ford, the first Ohio governor from the Western Reserve. Peter Hitchcock died in Painesville, Ohio, while stopped at the home of his eldest son on his way home from Columbus, Ohio to Burton. He was interred in Welton Cemetery, Burton, Ohio.
