Going back to January 20. Especially important or useful ones are bold.

• 2018 Homeland Security Appropriation, House Appropriations Committee bill language (July 19, 2017): page 9 (local link)
• 2018 Homeland Security Appropriation, House Appropriations Committee narrative report language (July 19, 2017): page 25 (local link)
• U.S. Customs and Border Protection congressional testimony on “Fiscal Year 2018 Budget Request” (June 13, 2017) (local link)
• Department of Homeland Security Office of Inspector General report “Lessons Learned from Prior Reports on CBP’s SBI and Acquisitions Related to Securing our Border” (June 12, 2017) (local link)
• 2018 Congressional Budget Justification, U.S. Customs and Border Protection including request for $1.571 billion to build 74 miles (May 23, 2017): page “CBP – PC&I – 48” (local link)
• Report by Democratic minority staff, Senate Homeland Security and Government Affairs Committee: “Southern Border Wall” (April 18, 2017) (local link)
• Department of Homeland Security draft “90-day Progress Report to the President on Executive Order 13767: Border Security and Immigration Enforcement Improvements” (April 12, 2017) (local link)
• U.S. Customs and Border Protection “pre-decisional” document: “Building the Wall: The Strategy and Way Forward” (March 27, 2017) (local link)
• U.S. Customs and Border Protection request for proposals for a “Solid Concrete Border Wall” (March 17, 2017) (local link)
• U.S. Customs and Border Protection request for proposals for an “Other Border Wall” (March 17, 2017) (local link)
• 2018 White House budget blueprint (also called “skinny budget”) requesting $1.571 billion to build 74 miles (March 16, 2017): page 23 (local link)
• 2017 White House revisions to budget request for $999 million to build 62 miles, which did not pass (March 16, 2017): page 6 (local link)
• Department of Homeland Security memorandum: “Implementing the President’s Border Security and Immigration Enforcement Improvement Policies” (February 20, 2017): page 5 (local link)
• U.S. Government Accountability Office report: “Southwest Border Security: Additional Actions Needed to Better Assess Fencing’s Contributions to Operations and Provide Guidance for Identifying Capability Gaps” (February 16, 2017) (local link)
• Congressional Research Service report: “Barriers Along the U.S. Borders: Key Authorities and Requirements” (January 27, 2017) (local link)
• White House Executive Order on Border Security and Immigration Enforcement Improvements (January 25, 2017) (local link)