The “Biophysical assessment for indemnity selection of federal lands in Colorado: Soil salinity using electrical conductance” dataset includes information on soil salinity for 89 Indemnity Units, comprising 339 parcels of federal lands. These lands, currently managed by the Bureau of Land Management (BLM), are under consideration for transfer of ownership to the State of Colorado in compensation for federal lands not available for transfer at the time of statehood. The Indemnity Units total 23,130 acres of surface and mineral estate and 6,150 acres of mineral estate only. The specific land parcels to be transferred to the State will be finalized after an environmental analysis is completed, as required by the National Environmental Policy Act (NEPA). This dataset summarizes information extracted from the Natural Resources Conservation Service (NRCS) gridded surface soils geographic database (gSSURGO). Fields retained and presented here include map unit (MU) codes and component (COMP) codes that may be used to reference records in the original NRCS data. Soil salinity is typically measured and evaluated based on electrical conductance (EC), and values presented here include the representative value for the map unit component (ECR) and the highest estimated value (ECH). Soils with high salinity can affect the composition of vegetation and can limit production of plants through effects on leaf water potential and water use efficiency. Elevated salinity is often created by geologic and soil moisture relations that promote movement of salts. Salt levels can increase as a result of cropping, irrigation and land management. Salinity is typically measured using electrical conductance in wet soils; soils with electrical conductance less than 2 millimhos (mmhos)/centimeter (cm) are non-saline, 2 to less than 4 mmhos/cm are very slightly saline, 4 to less than 8 mmhos/cm are slightly saline, 8 to less than 16 mmhos/cm are moderately saline, and greater than or equal to 16 mmhos/cm are strongly saline. Millimhos/centimeter is the traditional unit for soil EC measurement; it is equivalent to the accepted scientific unit, decisiemens/meter (dS/m). Only two Indemnity Unit had soils with electrical conductance greater than 8 mmhos/cm. NRCS SSURGO documentation should be consulted for details regarding soil mapping and estimation and application of EC (https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/home/?cid=nrcs142p2_053631). Review of information regarding EC and salinity from the source (NRCS) is suggested: https://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/home/?cid=nrcs144p2_065177 and/or https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_053280.pdf.