Rosecroft Raceway will open the earliest harness racing season in Maryland history Thursday. The 85-night meeting will conclude June 6, then racing will switch to Freestate Raceway in Laurel for 95 nights.

Post time at Rosecroft, a half-mile track in Oxon Hill, will be 8 p.m. for the first of 10 races.

The feature of the meeting again will be the William E. Miller Memorial Pace. The May 9 event is expected to carry a purse of $85,000, the biggest for a Maryland standardbred race. It is an open pace for 3-year-olds.

Earl Palmer Brown, local advertising executive and track president, said that more than $100,000 has been spent to improve the track since last year. The major project, he said, was reshaping the track to its original contours, which required 2,300 tons of bluestone dust.

Rosecroft again will feature three series of late-closing stakes races.

The Representative Pace for 3- and 4-year-olds drew 89 nominees and will be contested on five straight Thursday nights, starting opening night. The weekly purse will be $3,000, with the top finishers in the five legs racing in a $7,500 final April 4.

The Lady Legislator Race, with the first of three $3,500 legs leading to a $7,500 final March 23, is open to any mare or filly who won less than $20,000 in 1980.

The Senatorial Pace drew 33 nominees and has provided some of the most competitive races in recent years on Saturday nights. This series will include $7,500 legs every other week (Feb. 28, March 14 and 28).

Rosecroft will offer triple betting on the first and 10th races and exacta wagering on the second through ninth.