Both Uses

impede
in
The Masque of the Red Death
(Auto-generated)

...the folding doors slide back nearly to the walls on either hand, so that the view of the whole extent is scarcely impeded.
*

impeded = obstructed (made more difficult)
But from a certain nameless awe with which the mad assumptions of the mummer had inspired the whole party, there were found none who put forth hand to seize him; so that, unimpeded, he passed within a yard of the prince's person; and, while the vast assembly, as if with one impulse, shrank from the centres of the rooms to the walls, he made his way uninterruptedly, but with the same solemn and measured step which had distinguished him from the first, through the blue chamber to the purple—through the purple to the green—through the green to the orange—through this again to the white—and even thence to the violet, ere a decided movement had been made to arrest him.†

unimpeded = not slowed or blocked

standard prefix: The prefix "un-" in unimpeded means not and reverses the meaning of impeded. This is the same pattern you see in words like unhappy, unknown, and unlucky.

Definitions: