This data release consists of a comma-delimited ascii file with attributes for 21 U.S. Geological Survey streamgage sites in Hawai‘i and Southeast Alaska selected to enable assessment of how floods might change in a future climate. Floods in Hawai‘i and Southeast Alaska have led to loss of human life; damage to agricultural crops, cultural and biological resources, infrastructure, and property; threats to public health; and conditions that are highly disruptive to residents and visitors. Floods are generated by atmospheric and terrestrial processes that may be enhanced or depressed in response to climate change. Understanding the mechanisms that generate floods can be useful for assessing how floods may change in future climates and developing adaptive-management strategies to cope with future floods. Key to improved understanding of floods in Hawai‘i and Southeast Alaska is identifying sites that are affected by known flood-generating mechanisms and that can be used to potentially assess the effects of these mechanisms on the magnitude and frequency of floods, both historically and in a future climate. Stakeholders representing scientific, public-safety, cultural, and ecologic perspectives from government, academic, and private institutions provided input for developing and refining site-selection criteria and selecting sites. The site-selection criteria were: (1) the site contributes to representing the primary flood-generating mechanisms in the study area, (2) the site's available annual peak-streamflow record contains a minimum of 10 years of record during the 1980-2020 period, with a preference for longer records, (3) streamflow at the site during 1980-2020 was not substantively affected by regulation, urban areas, and basin land-use change, which could confound interpretation of the relation between floods and flood-generating mechanisms, (4) concurrent water years of annual peak-streamflow and daily mean streamflow records are available, which enables assessment of antecedent flood conditions, and (5) the site is preferably currently (2022) active, which indicates current relevance of the site’s data that could continue to be relevant in the future. The 21 selected sites are representative of classes of spatial climatic variations for Hawai‘i and seasonal and other flow regimes for Southeast Alaska. For Hawai‘i, selected sites consist of at least one site each from the drier (leeward) and wetter (windward) side of each of the five largest islands (Kaua‘i, O‘ahu, Moloka‘i, Maui, and Hawai‘i). For Southeast Alaska, selected sites consist of at least one site each from five seasonal streamflow regimes variously controlled by rain, snowmelt, and high-elevation melt (Curran and Biles, 2021), and one site each from flow regimes controlled by large basins and glacial lake outburst floods.