Time at the Top (1999)

Her building's elevator, having been altered by a retired physicist in the building, transports 14-year old Susan Shawson back in time from 1998 Philadelphia to the same place in 1881. There she meets Victoria Walker, a girl her own age in need of assistance with her own family's problems. Gradually discovering the power of her time machine, Susan, Victoria, and her young brother Robert travel back and forth in time and succeed in changing both the past and the future.