Obama was the 44th President of the United States, meaning there were 43 presidents who served before him took office in 2009. The numbering includes Grover Cleveland's non-consecutive terms as two separate presidencies.
Barack Obama was the 44th President of the United States. Since he was the 44th person to hold the office, exactly 43 presidents served before him. The marked answer of 44 incorrectly counts Obama himself among his predecessors.