He was prepared for college at Phillips Academy, in Andover, under the tuition of that highly distinguished scholar, Rev. Eliphalet Pearson. This eminent teacher was accustomed to say, that John Lowell, John Thornton Kirkland and William Symmes were the three brightest boys ever under his instruction. He graduated at Harvard College in 1780, after which he spent some time in Virginia as a private tutor. After pursuing a regular course of legal study in the office of that unrivalled jurist, Theophilus Parsons, in Newburyport, he was admitted to practise at the Essex bar. He immediately opened an office in the North Parish of Andover.

Mr. Symmes went to Portland in 1790; entered at once upon a successful practice, and took high rank at the bar.* He was a good classical scholar, a sound lawyer, and an able advocate. His manner was formal and stately, but graceful. A letter from one of his students says: "His personal appearance was stately and dignified. He was in all respects a gentleman in his manners, and emphatically one of the old school. He was affable and polite, and commanded affection as well as respect. He may truly be said to have been one of the most imposing and influential men at that time [1805] in Portland. As a lawyer and advocate he was unsurpassed. He had great discriminating powers; no one brought out the root and truth of the case so effectually as he did, whether at the bar or at any public meeting. Great confidence was felt in his opinions on all occasions, and especially on legal questions. He was unquestionably the best and most reliable lawyer of his time in the State."

Source:
- The Symmes memorial a biographical sketch of Rev. Zechariah Symmes By J.A. Vinton