After the war Simms practiced law in Alexandria, Virginia, and also collected taxes at the Port of Alexandria (Thompson Mason succeeding him in that office following Simms' death in 1819). Fairfax County voters elected Simms as one of their representatives in the
Virginia House of Delegates in 1785, 1786, 1792 and 1796. A staunch Federalist, Simms also represented Fairfax County in the
Virginia Ratifying Convention in 1788 that ratified the
United States Constitution, voters electing him and
David Stuart in a pointed rebuff the anti-ratification stance of
George Mason. He was a candidate for the
Electoral College in the
1796 United States presidential election, pledging to vote for
John Adams and
Patrick Henry. Reflecting his respect for Mason's insistence on a Bill of Rights similar to that Mason had drafted for Virginia, Simms served on the Virginia legislative committee that recommended amendments to the Constitution. In 1799, Simms successfully defended a land claim in the United States Supreme Court case ''
Irvine v. Sims's Lessee'' (his surname was misspelled in the official court records). Simms was an active
Mason as well as an acquaintance and associate of President
George Washington. He served as a pall bearer at Washington's funeral alongside fellow Masons and colonels who had served Washington: Dennis Ramsay, William Payne, George Gilpin,
Philip Marsteller and Charles Little. Simms also served on the board of directors of the Bank of Alexandria, the Little River Turnpike Comp[any, and the Marine Insurance Company. Alexandria voters elected Simms as
mayor in 1811. Still serving as such on August 29, 1814, Simms negotiated an arrangement with Captain James Gordon, whose frigate
Seahorse led a British armada up the Potomac River, anchored off Alexandria's port, and demanded all ships and cargo awaiting export. Alexandria merchants knew that the nearest Virginia militia, though about 1400 men under Brig. General John P. Hungerford, were about 24 miles away. In return for their agreeing not to burn the town, the British were allowed to restock their ships. They took 21 vessels, as well as 13,786 barrels of flour, 757 hogsheads of tobacco, and tons of cotton, tar, beef, sugar and other merchandise valued at $100,000 without a shot being fired. Thus, unlike Washington, D.C., Alexandria was not burned by British troops. Although censured for his actions (which some characterized as surrendering without a fight), Simms was later exonerated. ==Personal life==