David Logan (April 5, 1824 – March 26, 1874) was an American attorney and politician in the territory of and later state of Oregon. A native of Illinois, he moved to Oregon in 1850 where he served in the Oregon Territorial Legislature and in the Oregon Constitutional Convention. A founder of the Oregon Republican Party, he also served as mayor of Portland. David Logan was born in the state of Kentucky on April 5, 1824. The family later moved to the town of Springfield, Illinois. His father, Stephen T. Logan, practiced law as a partner with Abraham Lincoln in Springfield. David Logan studied law in Springfield under his father and Lincoln passing the bar in 1844 in Sangamon County. An anti-Democrat and Whig politically, Logan was to become a partner with Lincoln and his father in their practice before his drinking led to a falling out with his father. Due to this falling out, Logan's father sent him to join the army and fight in the Mexican-American War. David Logan also briefly moved to California. After Logan returned from the war, his father sent him to Oregon. In 1850, Logan arrived in what was then the Oregon Territory and set up a law practice in Lafayette.