The GOP in Congress are opening yet another investigation of Hillary Clinton's emails, or maybe its another one about Benghazi. Because all the previous investigations didn't find anything, dagnabbit! That prompted David Akadjian of Daily Kos to take a look at the history of Congressional investigations.
The Constitution doesn't mention investigations. There is a clause that Congress can make "all laws which shall be necessary and proper for carrying into execution the foregoing powers." So, to legislate effectively Congress needs to be able to gather background information.
There are limits. Congress can't poke into the affairs of a private individual unless it has something to do with the job of Congress. In addition, Congress does not do law enforcement or put people on trial (except for impeachments).
The first investigation was into the 1891 Battle of Wabash, in which 1000 men under General Arthur St. Clair were killed by Indians. Every major military engagement, except for the Spanish-American War of 1898 has led to Congressional investigations.
From about 1870 to WWI there were lots of economic abuses. Investigations led to reforms. After WWII Congress tended to investigate government. On the good side that was of procurement and construction for national defense. On the bad side that was the McCarthy hearings. Starting with Watergate there have been a series of investigations into political actors, including the Iran-Contra Affair.
But lately investigations have been a political tool. Bill Clinton was hit hard with these. Many disappear just after election day. These days it seems political investigations are endless, and usually fruitless.