[1] In late 1837, he married Rebecca Roberts of Alexandria, D.C.[citation needed] The Depot of Charts and Instruments was headed by Charles Wilkes.

The depot was responsible for the navy's chronometers, charts, and other navigational instruments and provided Gilliss with an opportunity to practice astronomy.

In 1837, he was named officer-in-charge of the depot and began an extensive series of observations of the moon and stars for the purpose of longitude determination.

[4] Gilliss continued working at the observatory, completing publication of his celestial catalog and providing support to the Office of Coast Survey.

In 1848, he obtained $5,000 from Congress for a naval astronomical expedition to Chile in order to more precisely measure the solar parallax.

The specimens of fauna and flora brought back from Chile formed the earliest part of the Smithsonian collection from Latin America.

[5] Gilliss later led two expeditions to observe the solar eclipses in Peru in 1858 and Washington Territory in 1860.

[citation needed] At the onset of the Civil War, Maury resigned to join the Confederate Navy and Gilliss was placed in charge of the observatory in 1861.

[3] His organization also played a crucial role in providing charts and navigation instruments to the rapidly expanding Union navy.