David Swinson "Doc" Maynard (March 22, 1808 – March 13, 1873) was an American doctor and businessman. He was one of Seattle's primary founders. Maynard was Seattle's first doctor, merchant prince, second lawyer, Sub-Indian Agent, Justice of the Peace, and architect of the Point Elliott Treaty of 1855.

Maynard was born to a family of means near Castleton, Vermont. At the age of 17 he was accepted into Castleton Medical School (which at the time was associated with Middlebury College). He was top in his class and apprenticed to Dr. Theodore Woodward (not to be confused with Dr. Theodore E. Woodward).

In 1828 he married Lydia A. Rickey; they had a daughter, Frances, in 1830 and a son, Henry, in 1834. According to court papers, he discovered in 1841 that she was unfaithful to him but remained with her until 1850.

In 1832, the Maynards moved to Cleveland, Ohio, at the time a town of 500. He made and lost small fortunes in business and political ventures including railroading and a medical school that collapsed in the Panic of 1837. Maynard left Cleveland in 1850, either promising to send for his family when he was settled elsewhere, or giving Lydia the chance to file for divorce on the grounds of desertion; either way, she never actually completed the divorce.

Maynard took the railroad to St. Louis, and from there set out for California. He circulated among several wagon trains fighting cholera, which he had learned about during the 1849 epidemic in Cleveland. When the leader of one small wagon train heading for Oregon Territory died, he assumed leadership and thus ended up on Puget Sound. He and widow Catherine Troutman Broshears (June 19, 1816 - Oct 20, 1906) fell in love during their journey; however, her brother, Mike Simmons, refused them permission to marry, perhaps on the grounds that Maynard was still married.

Maynard joined in the logging activity at New York-Alki (later Seattle), near the mouth of the Duwamish River on Puget Sound. Instead of selling his wood to shippers at $4 a cord, he leased a vessel from Captain Felker, using the wood itself as security, and sold the load in San Francisco at ten times the price. With that money, he bought the fixings for a general store and briefly set up in competition to the only other such store on Puget Sound, which was in Olympia and owned by Catherine's brother. Mike soon agreed to his sister marrying Maynard, apparently on condition that they move the store to Duwamps and do something about that prior marriage.

In April 1852, Maynard claimed, as a married man, a tract of land of 640 acres in what is now Seattle's Pioneer Square neighborhood, and hired Indians to help him build a combination cabin and store. According to historian Bill Speidel, the land he preferred was the undeveloped southern part of Carson Boren's claim, but while Boren was out of town, Arthur Denny shifted Carson's claim north to make room for Maynard. Maynard's building became a hub of activity when Maynard became King County's first Justice of the Peace.

Maynard laid out streets in his claim according to the cardinal directions (north/south) but Boren and Denny insisted on orienting the streets according to their stretch of shoreline. Seattle's downtown still shows awkward bends and jogs where the plats meet, but the rest of King County follows Maynard's original design. In reference to the disagreement Arthur Denny would go on to comment that "Maynard was king of all he surveyed, and some of what Boren and I surveyed as well." In a study conducted by the City of Seattle in the 1930s it was determined that Denny has platted his streets in violation of donation land claim law under which the original land claims were filed.