Information on past legislation:
Legislation from Congress.gov
Congressional Research Service Report: unbiased overview of issues, legislative histories
Government reports from Google Advanced Search .gov domain
Harvard Think Tank Search: Policy perspectives, issue overviews (usually biased) statistical analysis to support policy perspectives
Library Book Catalog: Longer coverage of the topic, can look at tables of contents to get overview or index to see coverage of specific issues
Information on party stances:
The Presidency Project - https://www.presidency.ucsb.edu/documents/app-categories/elections-and-transitions/party-platforms
The Republican National Committee - https://www.gop.com/about-our-party/
The Democratic Platform - https://democrats.org/where-we-stand/party-platform/
Information on public opinion data:
Bipartisan Policy Center: bipartisan-focused research and reports
Pew Research Center: unbiased research studies and statistical analysis
YouGov /Research Reality: public opinion data on covering various topics
Idenitfying and finding Federal elected officials
Find Your Representative | house.gov: database that helps you identify your congressional representatives based on zip code
U.S. Senate: Senators: database with information for all U.S. senators and how they can be contacted
Find Your Members in the U.S. Congress | Congress.gov | Library of Congress: database that allows you to locate your representatives and senators