Track Trends Original Track
| Year | Start | End | Days | Races | Avg. Att. | Avg. Han. |
| 1966 | April 16 | May 30 | 32 | 288 | 19,957 | 1,794,482 |
| October 12 | November 12 | 24 | 216 | 19,741 | 1,930,491 | |
| 1967 | April 22 | May 30 | 28 | 252 | 20,687 | 1,936,656 |
| October 14 | November 18 | 28 | 252 | 17,175 | 1,771,824 | |
| 1968 | April 23 | May 30 | 29 | 261 | 19,592 | 2,041,056 |
| October 14 | November 19 | 31 | 279 | 15,996 | 1,776,556 | |
| 1969 | April 23 | May 30 | 33 | 297 | 19,039 | 2,081,076 |
| October 15 | November 18 | 30 | 270 | 16,209 | 1,830,406 | |
| 1970 | April 20 | May 30 | 36 | 324 | 17,845 | 1,931,894 |
| October 19 | November 14 | 24 | 216 | 16,001 | 1,803,226 | |
| 1971 | April 17 | May 31 | 37 | 333 | 16,946 | 1,813,916 |
| October 19 | November 13 | 23 | 209 | 15,751 | 1,673,788 | |
| 1972 | April 22 | May 29 | 31 | 279 | 15,257 | 1,623,305 |
| October 17 | November 18 | 29 | 261 | 13,618 | 1,462,605 | |
| 1973 | March 10 | June 2 | 60 | 540 | 15,384 | 1,675,341 |
| 1974 | February 2 | May 27 | 75 | 676 | 10,944 | 1,624,492 |
| November 25 | December 31 | 31 | 279 | 6,463 | 749,084 | |
| 1975 | January 1 | February 28 | 49 | 443 | 7,942 | 885,750 |
| March 1 | May 27 | 73 | 657 | 7,942 | 885,750 | |
| 1976 | February 3 | June 10 | 111 | 999 | 11,480 | 1,362,705 |
| 1977 | February 1 | April 14 | 63 | 564 | 11,067 | 1,357,944 |