| San Luis Hills | |
|---|---|
 Sierro del Ojito in the Fairy Hills section of the San Luis Hills | |
| Highest point | |
| Elevation | 9,206 ft (2,806 m)[1] |
| Coordinates | 37°10′0″N105°44′32″W / 37.16667°N 105.74222°W /37.16667; -105.74222[2] |
| Dimensions | |
| Area | 428 sq mi (1,110 km2)[3] |
| Geography | |
 | |
| Location | San Luis Valley |
| Country | United States |
| State | Colorado |
TheSan Luis Hills[2] are a group of smallmountain ranges inConejos andCostilla counties in theSan Luis Valley in southernColorado.[4] The individual mountain ranges that make up the San Luis Hills include theFairy Hills, theBrownie Hills, thePiñon Hills, and theSouth Piñon Hills. The San Luis Hills' highest point isFlat Top, elevation 9,206 feet (2,806 meters).[1]
Each of the separate mountain ranges includes flat-topped mesas and hills, and the ranges trend from the southwest to the northeast.[4] Because the individual hills rise from the floor of the San Luis Valley, which is about 7,500 feet (2,300 meters) in elevation,[5] they appear more as hills than mountains, despite rising to eight or nine thousand feet above sea level.
The Hills are all within theSangre de Cristo National Heritage Area.[6]
The Fairy Hills lie at37°12′37″N105°45′14″W / 37.21028°N 105.75389°W /37.21028; -105.75389.[7] They are north ofColorado State Highway 142 and west of theRio Grande inConejos County.
The Brownie Hills lie at37°12′39″N105°42′50″W / 37.21083°N 105.71389°W /37.21083; -105.71389.[8] They are north ofColorado State Highway 142 and east of theRio Grande, inCostilla County.
The Piñon Hills lie at37°07′50″N105°49′02″W / 37.13056°N 105.81722°W /37.13056; -105.81722.[9] They are south ofColorado State Highway 142 and west of theRio Grande, inConejos County.
The South Piñon Hills lie at37°04′17″N105°48′31″W / 37.07139°N 105.80861°W /37.07139; -105.80861.[10] As their name indicates, they are south of the Piñon Hills inConejos County, and just north of theNew Mexico border.
The hills are the exposed parts of an intra-rifthorst. They are capped byMiocenebasalts of theHinsdale Formation.[11] The basalt is underlain byOligoceneandesite anddacite volcanic deposits of the lowerConejos Formation.[4]
The public lands in the San Luis Hills are not developed for recreation. However, some informal hiking trails exist, andmountain climbing andbouldering are possible, especially around the Manassa Dike on south side of Flat Top.[12]
The San Luis HillsWilderness Study Area occupies a 10,883-acre (4,404-hectare) tract of land in the Piñon Hills. The wilderness study area was established in 1980 and is owned by the Bureau of Land Management.[13]
In 2016, the Western Rivers Conservancy got funding from the Conservation Alliance to purchase a 17,019-acre (6,887-hectare) tract in the Brownie Hills on both sides of theRio Grande, some of it adjacent to or overlapping with the Rio Grande Natural Area. The plan is to transfer the land to Costilla County, which will manage it for wildlife habitat, agriculture, and public open space.[14]
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