<Tr> <Td> - elevation </Td> <Td> 1,919 ft (585 m) </Td> </Tr> <Tr> <Td> - coordinates </Td> <Td> 32 ° 59 ′ 04" N 110 ° 47 ′ 01" W ﻿ / ﻿ 32.98444 ° N 110.78361 ° W ﻿ / 32.98444; - 110.78361 Coordinates: 32 ° 59 ′ 04" N 110 ° 47 ′ 01" W ﻿ / ﻿ 32.98444 ° N 110.78361 ° W ﻿ / 32.98444; - 110.78361 </Td> </Tr> <P> San Pedro River is a northward - flowing stream originating about 10 miles (16 km) south of the international border south of Sierra Vista, Arizona, in Cananea Municipality, Sonora, Mexico . The river starts at the confluence of other streams (Las Nutrias and El Sauz) just east of Sauceda, Cananea . Within Arizona, the river flows 140 miles (230 km) north through Cochise County, Pima County, Graham County, and Pinal County to its confluence with the Gila River, at Winkelman, Arizona . It is the last major, free - flowing undammed river in the American Southwest, it is of major ecological importance as it hosts two - thirds of the avian diversity in the United States, including 100 species of breeding birds and 300 species of migrating birds . </P> <P> The first people to enter the San Pedro Valley were the Clovis people who hunted mammoth here from 10,000 years ago . The San Pedro Valley has the highest concentration of Clovis sites in North America . Some Clovis sites of note are the Lehner Mammoth - Kill Site, the Murray Springs Clovis Site and the Naco Mammoth - Kill Site . </P>

Where does the san pedro river start and end
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