Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| District | Incumbent | Party | First elected | Result | Candidates |
| --- | --- | --- | --- | --- | --- |
| Illinois 3 | Robert P. Hanrahan | Republican | 1972.0 | Lost re-election Democratic gain | Marty Russo (D) 52.6% Robert P. Hanrahan (R) 47.4% |
| Illinois 4 | Ed Derwinski | Republican | 1958.0 | Re-elected | Ed Derwinski (R) 59.2% Ronald A. Rodger (D) 40.8% |
| Illinois 6 | Harold R. Collier | Republican | 1956.0 | Retired Republican hold | Henry Hyde (R) 53.4% Edward V. Hanrahan (D) 46.6% |
| Illinois 9 | Sidney R. Yates | Democratic | 1964.0 | Re-elected | Sidney R. Yates (D) Unopposed |
| Illinois 10 | Samuel H. Young | Republican | 1972.0 | Lost re-election Democratic gain | Abner J. Mikva (D) 50.9% Samuel H. Young (R) 49.1% |
| Illinois 12 | Phil Crane | Republican | 1969.0 | Re-elected | Phil Crane (R) 61.1% Betty C. Spence (D) 38.9% |
| Illinois 19 | Tom Railsback | Republican | 1966.0 | Re-elected | Tom Railsback (R) 65.3% Jim Gende (D) 34.7% |
| Illinois 20 | Paul Findley | Republican | 1960.0 | Re-elected | Paul Findley (R) 54.8% Peter F. Mack (D) 45.2% |
| Illinois 23 | Melvin Price | Democratic | 1944.0 | Re-elected | Melvin Price (D) 80.5% Scott Randolph (R) 19.5% |
Question:
what year was the first elected incumbant Sidney R. Yates?
Answer:
1964.0