The President, Vice President and all civil officers of the United States, shall be removed from office on impeachment for, and conviction of, treason, bribery, or other high crimes and misdemeanors.. Thus, the operative legal standard to apply to an impeachment of a sitting President is treason, bribery, or other high crimes and misdemeanors..
http://litigation.findlaw.com/legal-system/presidential-impeachment-the-legal-standard-and-procedure.html
Radical Republican views gathered momentum in Congress and were in the majority by the end of 1865. In April of 1866, Congress enacted a Civil Rights Act in response to southern Black Codes. The Act granted new rights to native-born blacks, including the right to testify in court, to sue, and to buy property.
http://www.historyplace.com/unitedstates/impeachments/johnson.htm
Article II, Section 4, says that the President, Vice President, and all civil Officers of the United States—which includes judges—can be impeached. Members of Congress can be expelled by their own respective body. (See Article I, Section 5, Clause 2.)
http://www.heritage.org/constitution/articles/1/essays/11/impeachment
The House of Representatives has the sole power to impeach. Despite common usage, impeachment is only the first step in the process from removing a person from a federal office. If a simple majority of the House votes to impeach, the US Senate holds a trial to determine if removal from office is warranted by the charges raised by the House.
http://www.answers.com/Q/Which_house_of_congress_is_responsible_for_impeachment_proceedings
The Constitution does not specify how impeachment proceedings are to be initiated. Early in our history, a Member would rise on the floor of Congress and propose an impeachment, which would then be assigned to a committee. In recent years, Members of the House Judiciary Committee have initiated the proceeding and then made recommendations for the whole House's consideration.
http://www.heritage.org/constitution/articles/1/essays/11/impeachment
How Congress Sets the Rules for Impeachment. Both the U.S. House of Representatives and the U.S. Senate have the right to make their own rules governing their procedure, and to change those rules. Under current rules, the actual impeachment inquiry begins in the Judiciary Committee of the House of Representatives.
http://litigation.findlaw.com/legal-system/presidential-impeachment-the-legal-standard-and-procedure.html
Many in Congress wanted to keep Radical sympathizer, Secretary of War, Edwin M. Stanton, in Johnson's cabinet. The political feud between the President and Congress climaxed as Johnson sought to oust Stanton in violation of the Tenure of Office Act.
http://www.historyplace.com/unitedstates/impeachments/johnson.htm
Illinois Governor Rod Blagojevich is being impeached. How does the impeachment process work?On January 9, 2009, the Illinois House of Representatives impeached Governor Rod Blagojevich in a 114-1 vote. The decision was reaffirmed by the incoming legislature on January 14 in a 117-1 vote for impeachment.
https://www.legalzoom.com/articles/how-does-the-impeachment-process-work
17th U.S. President. About President Johnson: He was a self-educated man of humble origin who was Abraham Lincoln's vice president during his second term and became President upon the assassination of Lincoln in April of 1865. Born to a poor family in Raleigh, North Carolina, as a boy Johnson never attended school.
http://www.historyplace.com/unitedstates/impeachments/johnson.htm
The Illinois House of Representatives has the sole power to start  impeachment proceedings in Illinois. Once the impeachment process  is started, it ends with a trial in the… Senate. If convicted, the  person is removed from office.
http://www.answers.com/Q/Which_house_of_congress_is_responsible_for_impeachment_proceedings
who in congress is responsible for impeachment
In Congress, the House of Representatives is responsible for impeachment. The House of Representatives in Congress is responsible for impeachment.