I grew up in Leavenworth, Kansas--home to five prisons and the oldest fort west of the Mississippi. Interestingly, there is a Leavenworth Street in San Francisco...but the two are not related in any way.
Leavenworth--the town--was named after Colonel Henry Leavenworth, who established Fort Leavenworth in 1827. Fort Leavenworth remains the oldest active army post west of the Mississippi.
Leavenworth--the street--was named for Reverend Thaddeus M. Leavenworth, an Episcopalian minister and phyisician. He arrived in San Francisco in 1847 as chaplain of Stevenson's First New York Volunteer Regiment. He served as alcalde in 1848-1849.
Thus endeth the history lesson...