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Mann Gulch 01

United States United States Gulch

Mann Gulch

667 m of rock, cut by the Missouri River.

See the cutWhen to go

Montanabw · CC BY-SA 3.0

The cut

667 metres, to scale.

A slice through Mann Gulch where it is deepest and narrowest, measured on the Copernicus relief model every 30 m. Same scale as the landmark standing on the floor.

1,943 m1,758 m667 m11 km rim to rim5.0 kmvertical scale × 1.51,943 m1,758 m667 m11 km rim to rim5.0 kmvertical scale × 3.0

Standing on the floor, to scale: Great Pyramid · 139 m · Empire State · 443 m

Depth is measured to the lower rim; the width is from rim to rim. A 30 m relief model smooths the narrowest walls, so a slot canyon reads shallower than it is.

667m

Depth

measured on the 30 m relief model

11.4km

Rim to rim

measured on the 30 m relief model

36°

Steepest wall

average over 300 m, from the relief

1,090m

Floor altitude

Rim to floor

6 °C warmer at the bottom.

In July the afternoon reaches 30 °C on the floor, against 24 °C on the rim. The best months to hike are in September. The rim freezes at night from October to April. The wettest months are from May to June.

rim · 1,943 mfloor · 1,090 m
  1. 1°-5°Jan
  2. 2°-4°Feb
  3. 7°2°Mar
  4. 12°7°Apr
  5. 18°13°May
  6. 23°18°Jun
  7. 30°24°Jul
  8. 28°23°Aug
  9. 22°16°Sep
  10. 13°7°Oct
  11. 6°0°Nov
  12. 0°-5°Dec
Hike: SepFrost on the rim: Oct–AprWettest: May–Jun

Afternoon highs, 1991–2020 averages (NASA POWER) brought to the altitude of the rim and of the floor with the standard lapse rate (6.5 °C per 1 000 m). Shade, wind and rock change this on the day. Not a forecast.

Gulch in Lewis and Clark County, Montana

Mann Gulch is a gulch in United States, cut by the Missouri River. The relief model measures 667 m from the floor to the lower rim, and 853 m to the higher one. Rim to rim it is 11 km wide where the cut was taken.

Read more on Wikipedia

Getting there.

Plan the visit

Guided hikes, a bed nearby, a car.

Car hire at HLN airport (Helena)Discover CarsSee prices 

Some links above are affiliate links: if you book through them we may earn a commission, at no extra cost to you. It never changes what the data on this page says.

The river

The Missouri River runs highest from May to June.

The Missouri River carries about 175 m³/s on average here. It runs highest from May to June, fed by melting snow. It is lowest from September to December.

  1. 105 m³/sJan
  2. 166 m³/sFeb
  3. 201 m³/sMar
  4. 271 m³/sApr
  5. 377 m³/sMay
  6. 428 m³/sJun
  7. 289 m³/sJul
  8. 146 m³/sAug
  9. 64 m³/sSep
  10. 69 m³/sOct
  11. 50 m³/sNov
  12. 69 m³/sDec

From about 50 m³/s in the lowest month to 428 m³/s in the highest. Its basin above this point covers 43,728 km².

Follow the Missouri River from source to mouth on Riveryas

Estimate: long-term flow from the HydroATLAS model (WaterGAP, 1971–2000) shaped by the monthly rain, snow and temperature of the area (NASA POWER). Dams change it. Not a forecast.

From the sky.

The canyon from above, with the relief shaded, the line of the cut, the river and what people have mapped around it.

Mann Gulch seen from above (Sentinel-2) N 6 km

Sentinel-2 cloudless 2016 (EOX, CC BY 4.0), 24 × 24 km, north up. The line is the cut above. Points © OpenStreetMap contributors.

Around the canyon.

    • viewpoints within 5 km
    • marked hiking routes within 4 km
    • via ferrata routes within 4 km
    • climbing crags within 3 km
    • footbridges and suspension bridges within 3 km
    • rafting, canoe, kayak or canyoning spots within 4 km
    • swimming spots within 3 km
    • named waterfalls within 4 km
    • caves within 3 km
    • car parks within 3 km
    • information boards and visitor centres within 4 km
    • bus stops within 2 km
    • campsites within 8 km
    • hotels and guesthouses within 8 km
    • restaurants and cafés within 4 km

    Counted in OpenStreetMap, the map anyone can edit, around the floor of the canyon. A low number may just mean nobody has mapped it yet. © OpenStreetMap contributors (ODbL).

    Towns nearby

    • Helena Valley Northeast21 km in a straight line
    • Helena Valley Northwest21 km in a straight line

    In our other atlases

    What else is around Mann Gulch.

    The river that carved it, the waterfalls inside it, the mountains on the rim, the lakes, beaches and island nearby — from our six sister atlases, each with its own figures.

    Riveryas4 rivers in the canyon
    Missouri River3,726 km · 2,478 m³/sBayou St. JohnBee CreekDeer Creek
    Peakyas13 mountains within 15 km
    Cap Mountain2,059 m · 3.6 kmBeartooth Mountain · 6.3 kmRattlesnake Mountain · 9.7 kmDevils Tower · 9.8 kmCandle Mountain · 10 kmCopper Butte · 12 kmJackson Peak · 13 kmMoors Mountain · 13 km

    Figures from the sister sites' databases (Wikidata, HydroATLAS, GeoNames, NOAA, OpenStreetMap). Links open when each site is online.

    Month by month

    The weather, at the floor and at the rim.

    JanFebMarAprMayJunJulAugSepOctNovDec
    Afternoon · floor1271218233028221360
    Afternoon · rim-5-427131824231670-5
    Night · rim-14-14-9-6-14872-4-9-14
    Rain (mm)313338587384343843393334
    Rainy days10101114141598810910
    Sun hours/day4.56.16.77.48.610.112.110.27.95.94.33.5
    Snow on the ground (cm)181714124100281518
    Afternoon · floorAfternoon · rimNight · rimRain (mm)Sun hours/day
    Jan1-5-14314.5
    Feb2-4-14336.1
    Mar72-9386.7
    Apr127-6587.4
    May1813-1738.6
    Jun231848410.1
    Jul302483412.1
    Aug282373810.2
    Sep22162437.9
    Oct137-4395.9
    Nov60-9334.3
    Dec0-5-14343.5

    Averages 1991–2020 (NASA POWER) for a cell about 55 km wide, brought to the floor (1,090 m) and the rim (1,943 m) with the standard lapse rate. Not a forecast.

    Photographs

    Seen from the trail.

    Mann Gulch 04
    Montanabw · CC BY-SA 3.0
    Bottom of Mann Gulch 5.1.13 (8902734505)
    Forest Service Northern Region from Missoula, MT, USA · Public domain
    Looking down Mann Gulch on left (8902721589)
    Forest Service Northern Region from Missoula, MT, USA · Public domain

    Recent years

    Wet years, dry years.

    Rain of each month as a share of the 1991–2020 average. A dry year means a lower river and hotter rock; a wet one, more water in the gorge.

    JanFebMarAprMayJunJulAugSepOctNovDec
    202088%104%84%78%105%206%77%38%61%152%91%45%
    202157%117%48%68%162%22%76%176%17%52%63%103%
    202272%61%70%77%59%79%182%126%135%133%110%94%
    202396%84%116%110%98%142%55%125%187%110%45%31%
    202459%148%76%92%116%70%56%104%168%21%82%81%
    202589%114%95%66%107%59%153%121%50%99%77%172%

    130% or more: wet month 70% or less: dry month

    Compare with the neighbours.

    Mann Gulch

    United States

    • 667 mDepth
    • 11 kmRim to rim
    • —Length
    • 36°Steepest wall

    Golden Gate Canyon

    United States · 232 km

    • 478 mDepth
    • 5.7 kmRim to rim
    • —Length
    • 31°Steepest wall

    See the guide

    Grand Canyon of the Yellowstone

    United States · 262 km

    • 301 mDepth
    • 1.7 kmRim to rim
    • —Length
    • 42°Steepest wall

    See the guide

    Burke Canyon

    United States · 309 km

    • 774 mDepth
    • 12 kmRim to rim
    • —Length
    • 35°Steepest wall

    See the guide

    Where these figures come from

    Name, type, published depth and lengthWikidata (Q6750678) · CC0
    The cut: depth, width, wall and 3D modelCopernicus DEM GLO-30 · © DLR e.V., © Airbus Defence and Space GmbH, Copernicus/ESA
    River flow and basinHydroATLAS / RiverATLAS v1.0 (Linke et al. 2019) · CC BY 4.0
    ClimateNASA POWER, 1991–2020
    Viewpoints, trails, bridges and the river line© OpenStreetMap contributors · ODbL
    ImagesEOX Sentinel-2 cloudless 2016 · CC BY 4.0; Wikimedia Commons
    Rivers, waterfalls, mountains, lakes, beaches and islands nearbyCoastya, Lakeyas, Peakyas, Cascadyas, Islandyas, Riveryas

    Every figure is an average, an estimate or a count from a public dataset. Licences and methods: data sources.

    The family

    Do you prefer beaches, lakes, mountains, waterfalls, islands, rivers or canyons?

    Same idea, other landscapes: field atlases built on open data, month by month, in seven languages.

    beachesCoastyaFind your beach: sea temperature, sun and swimming month by month.Visit
    lakesLakeyasEvery lake on Earth: water temperature, ice, depth and the shore.Coming soonVisit
    mountainsPeakyasEvery summit in 3D: summit weather, the 0 °C line, huts and trails.Visit
    waterfallsCascadyasEvery waterfall: height, flow month by month and when it roars.Coming soonVisit
    islandsIslandyasEvery island from the sea up: size, sea temperature, ferries and 3D.Visit riversRiveryasEvery river from source to sea: the journey, the flow and the basin in numbers.Visit
    canyonsCanyonyasEvery canyon cut to scale: depth to the floor, rim and floor temperatures, trails and viewpoints.You are here