The history of landscape architecture  is related to the history of gardening but is not coextensive.  Both arts are concerned with the composition of planting, landform, water, paving and other structures but:

• Garden design is essentially concerned with enclosed private space
• Landscape design is concerned with the design of enclosed space, as well as unenclosed space which is open to the public

The Romans undertook landscape architecture on an extensive scale, and Vitruvius wrote on many topics which still concern landscape architects.  As with the other arts, it was not until the Renaissance that garden design was revived, with outstanding examples including the pleasure grounds at the Villa d'Este, Tivoli.  The renaissance garden developed through the 16th and 17th centuries, reaching an ultimate grandeur in the work of Andr'e le Notre at Vauz-le-Vicomte and Versailles.

Central Park in New York

In the 18th century, England became the focus of a new style of landscape design.  Figures such as William Kent, Humphry Repton, and most famously Lancelot 'Capability' Brown remodeled the great estate parks of the English gentry to resemble a neat and tidy version of nature.  Many of these parks remain today.  The term 'landscape architecture' was first used by the Scotsman Gilbert Laing Meason in the title of his book on The Landscape Architecture of the Great Painters of Italy (London, 1828).  It was about the type of architecture found in landscape paintings.  The term "landscape architecture" was then taken up by J.C Loudon and A.J Downing.

Through the 19th century, urban planning became more important, and it was the combination of modern planning with the tradition of landscape gardening that gave Landscape Architecture its unique focus.  In the second half of the century, Frederick Law Olmsted completed a series of parks which continue to have a huge influence on the practices of Landscape Architecture today.  Among these were Central Park in New York, Prospect Park in Brooklyn, and Boston's so-called Emerald Necklace park system.

The Emerald Necklace Park System in Boston

Landscape architecture continues to develop as a design discipline, and has responded to many of the movements of design and architecture through the 20th century.  Today, a healthy level of innovation continues to provide challenging design solutions for streetscapes, parks and gardens.  The work of Martha Schwarz in the US, and in Europe designs such as Schouwburgplein in Rotterdam by the Dutch design group West 8 are just two examples.

Schouwburgplein in Rotterdam

Ian McHarg is considered an important influence on the modern Landscape Architecture profession and land planning in particular.  With his book "Design with Nature", he popularized a system of analyzing the layers of a site in order to compile a complete understanding of the qualitative attributes of a place.  This system became the foundation of today's Geographic Information Systems (GIS).  McHarg would give every qualitative aspect of the site a layer such as the history, hydrology, topography, vegetation, etc.  GIS software is ubiquitously used in the landscape architecture profession today to analyze materials in and on the earth's surface and is similarly used by Urban Planners, Geographers, Forestry and Natural Resources professionals, etc.

-Wikipedia